PSIA Volume. 16 Series Mass and Volumetric Flow Controllers Mass and Volumetric Flow Controllers

Transcription

1 Alicat Scientific Set Point - Process Alicat Scientific PSIA Volume C Mass Set Pt CCM Air Main MODE SLPM L H Set Point Local Set Point Module Alicat Scientific Alicat Scientific, Inc. PSIA C Set Pt CCM Air Volume Mass Main MODE Alicat Scientific, Inc. FLOW 16 Series 16 Series Mass and Volumetric Flow Controllers Mass and Volumetric Flow Controllers Precision Gas Flow Controller Operating Manual Precision Gas Flow Controller Operating Manual 1

2 Notice: Alicat Scientific, Inc. reserves the right to make any changes and improvements to the products described in this manual at any time and without notice. This manual is copyrighted. This document may not, in whole or in part, be copied, reproduced, translated, or converted to any electronic medium or machine readable form, for commercial purposes, without prior written consent from the copyright holder. Note: Although we provide assistance on Alicat Scientific products both personally and through our literature, it is the complete responsibility of the user to determine the suitability of any product to their application. The manufacturer does not warrant or assume responsibility for the use of its products in life support applications or systems. 8/21/03 Rev. 1 DOC-ALIMAN16C 2

3 Table of Contents Page Introduction 1 Flow Measurement Operating Principle 1 Flow Control Operating Principle 2 Understanding Volumetric and Mass Flow 2 Gas Viscosity 3 Other Gases 3 Volumetric Flow vs. Mass Flow 3 Volumetric Flow and Mass Flow Conversion 4 Installation 6 Plumbing 6 Mounting 6 Application 6 Power and Signal Connections 7 VC Series Volumetric Flow Controller Operations 12 Main Mode 12 MODE 12 Volume 12 Set Pt 12 Control Setup Mode 13 Input 13 Select 14 Gas Select Mode 15 Identity Mode 15 Volumetric Flow Meters Under Pressure 16 MC Series Mass Flow Controller Operations 17 Main Mode 17 MODE 17 Set Pt 17 Gas Absolute Pressure 17 Gas Temperature 18 Volumetric Flow Rate 18 Mass Flow Rate 18 Control Setup Mode 18 Input 18 Loop 19 Select 19 Gas Select Mode 20 Identity Mode 3 20

4 Table of Contents continued Page RS-232 Output and Input 21 Configuring Hyperterminal 21 Data Format 21 Sending a Set Point via RS To Adjust the Proportional and Differential (P&D) Terms via RS Collecting Data 23 Changing from Streaming to Polling Mode 23 Selecting a Gas 24 Sending a Simple Script File to HyperTerminal 25 Options 26 Totalizing Mode Screen 26 Troubleshooting 27 Maintenance and Recalibration 29 Warranty 29 Additional Information 30 Accessories 30 Gas Viscosity Table 30 Flow Conversion Table 30 Gas Density Conversion Table 31 Performance Specifications 32 Conformity / Supplemental Information 32 Mounting Holes 33 Table of Figures Page Figure 1. 8 Pin Mini-DIN Connector 7 Figure 2. Mini-DIN to DB-9 Connection for RS-232 Signals 10 Figure 3. Typical Multiple Device (Addressable) Wiring Configuration 10 Figure 4. Optional Industrial Connector 11 Figure 5. Main Mode Display, VC Series Flow Meter 12 Figure 6. VC Series Control Setup Mode Screen 13 Figure 7. Gas Select Mode 15 Figure 8. Identity Mode 15 Figure 9. Main Mode Display, MC Series Flow Meter 17 4

5 Introduction Thank you for purchasing a VC or MC Series Gas Flow Controller Please take the time to find and read the pertinent information contained in this manual for your specific device. This will help to ensure that you get the best possible service life from your instrument. This manual covers the following Alicat Scientific, Inc. instruments: VC Series 16 Bit Volumetric Gas Flow Controllers MC Series 16 Bit Mass Gas Flow Controllers VC-XXCCM-D VC-XXLPM-D MC-XXSCCM-D MC-XXSLPM-D The 16 Series data presentation format utilizes a full graphic display that allows simultaneous viewing of all operating parameters. The dynamically labeled display allows the user to make field adjustments to the set point, the P (proportional) and D (derivative) loop control terms, and in some cases actually close the control loop on different parameters right on the unit. Selected parameters can be toggled to the large primary display for ease of viewing. Flow Measurement Operating Principle All VC or MC Series Gas Flow Controllers are based on the accurate measurement of volumetric flow. The volumetric flow rate is determined by creating a pressure drop across a unique internal restriction, known as a Laminar Flow Element (LFE), and measuring differential pressure across it. The restriction is designed so that the gas molecules are forced to move in parallel paths along the entire length of the passage; hence laminar (streamline) flow is established for the entire range of operation of the device. Unlike other flow measuring devices, in laminar flow controllers the relationship between pressure drop and flow is linear. The underlying principle of operation of the 16 Series Flow Controllers is known as the Poiseuille Equation: Q = (P 1 -P 2 )πr 4 /8ηL (Equation 1) Where: Q P 1 P 2 r η L = Volumetric Flow Rate = Static pressure at the inlet = Static pressure at the outlet = Radius of the restriction = (eta) absolute viscosity of the fluid = Length of the restriction Since π, r and L are constant; Equation 1 can be rewritten as: Q = K ( P/η) (Equation 2) Where K is a constant factor determined by the geometry of the restriction. Equation 2 shows the linear relationship between volumetric flow rate (Q) differential pressure ( P) and absolute viscosity (η) in a simpler form. 1

6 Flow Control Operating Principle For the purposes of this explanation, the term valve will refer to the proportional control valve mounted on the controller. The term controller will refer to the flow meter and the measurement and control electronics portion of the device. In actuality, the whole device is generally referred to as a controller. The valve may be mounted either upstream or downstream of the controller depending upon the application. VC and MC Series flow controllers ship with a normally closed proportional control valve. Flow is closed off by a mechanical spring, which holds an elastomer tipped plunger on an appropriately sized flow orifice called a seat. No flow will occur until the valve receives a voltage signal from the controller, and the controller will not send a voltage signal to the valve until the user provides a set point to the controller. The user can provide a set point either locally via the display and user interface buttons, or more commonly, by providing an external signal that corresponds to the flow range of the controller. This external signal can be an analog voltage or current signal such as a 0-5 Vdc or 4-20 ma signal, or a digital RS-232 signal via serial communication with a computer. The controller utilizes what is called PID (Proportional, Integral, Derivative) loop control circuitry and software. The PID loop control works by repeatedly comparing the measured flow rate to the set point and incrementally adjusting the voltage signal to the valve in a continuous attempt to match the measured flow rate to the set point. For example, at any given time the controller looks at the measured flow rate and the set point, if the set point is higher than the measured flow rate, the controller will slightly increase the voltage signal to the valve and thus open it little more. If the set point is lower than the measured flow rate, the controller will slightly decrease the voltage signal to the valve and thus close it off a little more. This look, compare, and adjust loop occurs on the order of 1000 times each second. VC and MC Series flow controllers ship with a general PID tuning that is usually sufficient for most applications. Occasionally an application will require the customer to change this tuning. The Proportional and Derivative terms can be field adjusted in all MC and VC controllers. In very general terms, the P term can be thought of as how fast the controller responds to change and the D term can be thought of as a dampening factor. Understanding Volumetric and Mass Flow In order to get an accurate volumetric flow rate reading from your controller, the gas being measured must be selected in the gas select mode. This is important because the device calculates the flow rate based on the viscosity of the gas at the measured temperature. If the gas being measured is not what is selected, an incorrect value for the viscosity of the gas will be used in the calculation of flow, and the resulting output will be inaccurate in direct proportion to the difference in the two gases viscosities. 2

7 Gas Viscosity: In order to get an accurate volumetric flow rate, the gas being measured must be selected (see Gas Select Mode page 11). This is important because the device calculates the flow rate based on the viscosity of the gas at the measured temperature. If the gas being measured is not what is selected, an incorrect value for the viscosity of the gas will be used in the calculation of flow, and the resulting output will be inaccurate in direct proportion to the difference in the two gases viscosities. Gas viscosity, and thus gas composition, can be very important to the accuracy of the meter. Anything that has an effect on the gas viscosity (e.g. water vapor, odorant additives, etc.) will have a direct proportional effect on the accuracy. Selecting methane and measuring natural gas for instance, will result in a fairly decent reading, but it is not highly accurate because natural gas contains small and varying amounts of other gases such as butane and propane that result in a viscosity that is somewhat different than pure methane. Absolute viscosity changes very little with pressure therefore a true volumetric reading does not require a correction for pressure. Changes in gas temperature do affect viscosity. For this reason, the MC Series utilizes the temperature sensor to internally compensate for this change and no outside temperature correction is required for volumetric measurement. Other Gases: MC Series Flow Controllers can easily be used to measure the flow rate of gases other than those listed as long as non-corrosive" gas compatibility is observed. For example, a flow meter that has been set for air can be used to measure the flow of argon. The conversion factor needed for measuring the flow of different gases is linear and is simply determined by the ratio of the absolute viscosity of the gases. This factor can be calculated as follows: Q og = Q 1 [η 1 / η og ] Where: Q 1 = Flow rate indicated by the flow meter η 1 = Viscosity of the calibrated gas at the measured temp. Q og = Flow rate of the alternate gas η og = Viscosity of the alternate gas at the measured temp. A good rule of thumb is at a given flow rate, the higher the viscosity, the higher the indicated flow Volume Flow vs. Mass Flow: At room temperature and low pressures the volumetric and mass flow rate will be nearly identical, however, these rates can vary drastically with changes in temperature and/or pressure because the temperature and pressure of the gas directly affects the volume. For example, assume a volumetric flow reading was used to fill balloons with 250 ml of helium, but the incoming line ran near a furnace that cycled on and off, intermittently heating the incoming helium. Because the volumetric meter simply measures the volume of gas flow, all of the balloons would initially be the same size. However, if all the balloons are placed in a room and allowed to come to an equilibrium temperature, they would generally all come out to be different sizes. If, on the other hand, a mass flow reading were used to fill the balloons with 250 standard ml of helium, the resulting balloons would initially be different sizes, but when allowed to come to an equilibrium temperature, they would all turn out to be the same size. 3

8 This parameter is called corrected mass flow because the resulting reading has been compensated for temperature and pressure and can therefore be tied to the mass of the gas. Without knowing the temperature and pressure of the gas and thus the density, the mass of the gas cannot be determined. Once the corrected mass flow rate at standard conditions has been determined and the density at standard conditions is known (see the density table at the back of this manual), a true mass flow can be calculated as detailed in the following example: Mass Flow Meter Reading = 250 SCCM (standard Cubic Centimeters/min) Gas: Helium Gas Density at 25C and PSIA =.1636 grams/liter True Mass Flow = (Mass Flow Meter Reading) X (Gas Density) True Mass Flow = (250 CC/min) X (1 Liter/ 1000 CC) X ( grams/liter) True Mass Flow = grams/min of Helium Volumetric and Mass Flow Conversion: In order to convert volume to mass, the density of the gas must be known. The relationship between volume and mass is as follows: Mass = Volume x Density The density of the gas changes with temperature and pressure and therefore the conversion of volumetric flow rate to mass flow rate requires knowledge of density change. Using ideal gas laws, the effect of temperature on density is: ρ a / ρ s = T s / T a Where: ρ a = ambient condition T a = absolute ambient condition in Kelvin ρ s = standard (reference ) condition T s = absolute standard (reference) condition in Kelvin ºK = ºC Note: ºK=ºKelvin The change in density with pressure can also be described as: ρ a / ρ s = P a / P s Where: ρ a = ambient condition P a = ambient absolute pressure ρ s = standard (reference ) condition P s = Absolute standard (reference) condition Therefore, in order to determine mass flow rate, two correction factors must be applied to volumetric rate: temperature effect on density and pressure effect on density. Although the correct units for mass are expressed in grams, kilograms, etc. it has become standard that mass flow rate is specified in SLPM (standard liters / minute), SCCM (standard cubic centimeters / minute) or SmL/M (standard milliliters / minute). 4

9 This means that mass flow rate is calculated by normalizing the volumetric flow rate to some standard temperature and pressure (STP). By knowing the density at that STP, one can determine the mass flow rate in grams per minute, kilograms per hour, etc. STP is usually specified as the sea level conditions; however, no single standard exists for this convention. Examples of common reference conditions include: 0 C and PSIA 25 C and PSIA 0 C and 760 torr (mmhg) 70 F and PSIA 68 F and inhg 20 C and 760 torr (mmhg) MC Series Flow Controllers reference 25ºC and PSIA (101.32kPa) - unless ordered otherwise. Refer to the calibration sheet to confirm the reference point. 5

10 Installation Plumbing All VC or MC Series Gas Flow Controllers are equipped with female inlet and outlet port connections. Because the flow meters set up a laminar flow condition within the flow body, no straight runs of pipe are required upstream or downstream of the meter. The inlet and outlet ports are equal in size and symmetric (in-line). Normally speaking, the port sizes and dimensions for differing flow ranges are as follows: Flow Range Height Length Depth Port Size.5 to 50 (S)CCM (S)CCM to 20 (S)LPM ⅛ NPT(F) 20+ to 100 (S)LPM ¼ NPT(F) 100+ to 250 (S)LPM ½ NPT(F) 250+ to 1000 (S)LPM ¾ NPT(F) Meters with ports have o-ring face seals and require no further sealant or tape. Avoid the use of pipe dopes or sealants on the ports as these compounds can cause permanent damage to the meter should they get into the flow stream. Use of thread sealing Teflon tape is recommended to prevent leakage around the threads. When applying the tape, avoid wrapping the first thread or two to minimize the possibility of getting a piece of shredded tape into the flow stream. When changing fittings, always clean any tape out of the threads that may come loose and enter the flow stream. In addition, it is recommended that a 20 micron filter be installed upstream of meters with full scale ranges of 1 (S)LPM or less and a 50 micron filter be installed upstream of meters with full scale ranges above 1 (S)LPM. Mounting All VC or MC Series Gas Flow Controllers have mounting holes in their meters for convenient mounting to flat panels. Some valve/meter combinations may require spacer blocks to mount to flat surfaces. The sizes and dimensions for these holes are shown on pages 33 to 37 of this manual. Please note that there are many different possible controller configurations and that the diagram shows only the footprint and mounting holes in the meter flow body. Position sensitivity is not generally an issue with small valve controllers. Large valve controllers, however, are somewhat position sensitive because of the fairly massive stem assembly and it is generally recommended that they be mounted so that the valve cylinder is vertical and upright. The primary concern in mounting a large valve controller in a position other than the recommended position is the increased risk of leakage when the controller is given a zero set point and is being held closed by the spring force. Application Maximum recommended operating line pressure is 125 PSIG (862 kpa). Caution: Exceeding 150 PSI line pressure may cause permanent damage to the solid-state differential pressure transducer. If the line pressure is higher than the 125 PSIG (862 kpa), a pressure regulator should be used upstream from the flow controller to reduce the pressure to 125 PSIG (862 kpa) or less if 6

11 possible. Many of our controllers are built after extensive consultations with the customer regarding the specific application. The result is that two controllers with the same flow range and part number may look and act quite differently depending upon the application the controller was built for. Care should be taken in moving a controller from one application to another to test for suitability in the new application. Note that volumetric meters and controllers are not recommended for high pressure or high backpressure applications. Power and Signal Connections Power can be supplied to your VC or MC Series meter through either the AC/DC adapter jack, or through the 8 pin Mini-DIN connector as shown in Figure 1. Small Valve: If your controller utilizes a small valve (about the size of your thumb), a Vdc power supply with a P-5 style, positive center plug capable of supplying 300 ma is recommended. Large Valve: If your controller utilizes a large valve (about the size of your fist), a 24 Vdc power supply with a P-5 style, positive center plug capable of supplying at least 750mA is required. These are commonly available at local electronics suppliers. Alternatively, power can be supplied through the Mini-DIN connector as shown below: AC/DC Adapter Jack Figure 1. 8 Pin Mini-DIN Connector 7

12 Pin Function DC-61 (optional) Color Code mA Output Signal Black Vdc or Auxiliary Output Brown 3 RS-232 Input Signal Red 4 Analog Input Signal Orange 5 RS-232 Output Signal Yellow Vdc (or 0-10 Vdc) Output Signal Green 7 Power In (9-30 Vdc, 100mA) Blue 8 Ground (common) Purple Note: The above pin-out is applicable to all the flow meters and controllers available with the mini din connector. The availability of different output signals depends on the Flow Controller options ordered. CAUTION: Do not connect power to pins 1 through 6 as permanent damage can occur! Signal Connections: Analog Input Signal Apply analog input to Pin 4 as shown in Figure 1. Standard 0-5 Vdc: Unless ordered otherwise, 0-5 Vdc is the standard analog input signal. Apply the 0-5 Vdc input signal to pin 4, with common ground on pin 8. Optional 0-10 Vdc: If specified at time of order, a 0-10 Vdc input signal can be applied to pin 4, with common ground on pin 8. Optional 4-20 ma: If specified at time of order, a 4-20 ma input signal can be applied to pin 4, with common ground on pin 8. RS-232 Digital Input Signal If you will be using the RS-232 output signal, it is necessary to connect the RS-232 Output Signal (Pin 5), the RS-232 Input Signal (Pin 3), and Ground (Pin 8) to your computer serial port as shown in Figure 2. Adapter cables are available from the manufacturer or they can be constructed in the field with parts from a local electronic supply house. In Figure 2, note that the diagrams represent the port side of the connections, i.e. the connector on top of the meter and the physical DB-9 serial port on the back of the computer. The cable ends will be mirror images of the diagram shown in Figure 2. (See page 21 for details on accessing RS-232 output and input.) 8

13 Analog Output Signals: **Note** Upon initial review of the pin out diagram in Figure 1, it is common to mistake Pin 2 (labeled 5.12 Vdc Output) as the standard 0-5 Vdc analog output signal! In fact Pin 2 is normally a constant 5.12 Vdc that reflects the system bus voltage and can be used as a source for the input signal. This allows the user in the field to run this output through a 50K ohm potentiometer and back into the analog set point pin to create a 0-5 Vdc set point source. Standard Voltage (0-5 Vdc) Output Signal All VC and MC Series Flow Controllers have a 0-5 Vdc (optional 0-10 Vdc) output signal available on Pin 6. This is generally available in addition to other optionally ordered outputs. This voltage is usually in the range of Vdc for zero flow and 5.0 Vdc for full-scale flow. The output voltage is linear over the entire range. Ground for this signal is common on Pin 8. Optional 0-10 Vdc Output Signal If your meter was ordered with a 0-10 Vdc output signal, it will be available on Pin 6. (See the Calibration Data Sheet that shipped with your meter to determine which output signals were ordered.) This voltage is usually in the range of Vdc for zero flow and 10.0 Vdc for fullscale flow. The output voltage is linear over the entire range. Ground for this signal is common on Pin 8. Optional Current (4-20 ma) Output Signal If your meter was ordered with a 4-20 ma current output signal, it will be available on Pin 1. (See the Calibration Data Sheet that shipped with your meter to determine which output signals were ordered.) The current signal is 4 ma at 0 flow and 20 ma at the meter s full scale flow. The output current is linear over the entire range. Ground for this signal is common on Pin 8. This output always tracks the same variable as the standard output. Optional 2nd Analog Output Signal You may specify an optional 2 nd analog output on Pin 2 at time of order. (See the Calibration Data Sheet that shipped with your meter to determine which output signals were ordered.) This output may be a 0-5 Vdc, 0-10 Vdc, or 4-20 ma analog signal that can represent any measured parameter. With this optional output, a volumetric flow controller could output the volumetric flow rate with a 0-5 Vdc signal (on pin 6) and a 4-20 ma signal (on pin 2), or a mass flow controller could output the mass flow rate (0-5 Vdc on pin 6) and the absolute pressure (0-5 Vdc on pin 2). This ability makes these devices exceedingly versatile. RS-232 Digital Output Signal If you will be using the RS-232 output signal, it is necessary to connect the RS-232 Output Signal (Pin 5), the RS-232 Input Signal (Pin 3), and Ground (Pin 8) to your computer serial port as shown in Figure 2. Adapter cables can be constructed in the field with parts from a local electronic supply house. In Figure 2, note that the diagrams represent the port side of the connections, i.e. the connector on top of the controller and the physical DB-9 serial port on the back of the computer. The cable ends will be mirror images of the diagram shown in Figure 2. 9

14 DB-9 Serial Port 8 Pin Mini-DIN Port Ground Ground Transmit Receive Receive Transmit Figure 2. Mini-DIN to DB-9 Connection for RS-232 Signals Purple Red Yellow Unit A Purple Red Yellow Unit B Purple Red Yellow Unit C Alicat Scientific typical multiple device RS-232 Connection Ground Transmit > Receive < Female Serial Cable Front Figure 3. Typical Multiple Device (Addressable) Wiring Configuration 10

15 An optional industrial connector is also available: Pin Function 1 Power In 2 RS-232 Output 3 RS-232 Input Signal 4 Analog Input Signal 5 Ground 6 Signal Out (Voltage or Current as ordered) Figure 4. Optional Industrial Connector Note: The above pin-out is applicable to all flow meters and controllers ordered with the industrial connector. The availability of different output signals depends on the options ordered. 11

16 VC Series Volumetric Flow Controller Operation The VC Series Volumetric Flow Controller is a simple, rugged device. The membrane switch user interface and dynamically labeled graphic display combine to provide exceedingly flexible and user-friendly operation. The VC Series has several screen modes. All VC Series Controllers with a display have a default Main Mode, a Control Setup Mode, a Gas Select Mode, and an Identity Mode. Each mode is described below. The device defaults to Main Mode as soon as power is applied to the controller. Main Mode The main mode screen shows the volumetric flow in the units specified at time of order. In the main mode, only two buttons are active as shown in Figure 5. The process gas that is selected is shown directly under the flow units. Set Pt 0.00 CCM 0.00 Air Volume Main MODE Figure 5. Main Mode Display, VC Series Flow Controller MODE - The MODE button in the lower right hand corner toggles the display between modes. Volume The volume flow rate is defaulted on the primary display. If the set point has been toggled to the primary screen as described below, the volume flow rate can be toggled back to the primary display by pushing the button (lower left corner) directly beneath the dynamic label Volume. Set Pt The set point is shown in the upper right corner of the display. The set point cannot be adjusted from the main mode screen. For information on changing the set point, see the Control Set Up Mode below. 12

17 Control Setup Mode The Control Setup Mode is accessed by pressing the button labeled MODE until the dynamic label over the button reads Control Setup as shown in Figure 6 below. This mode allows the user to set up most parameters commonly associated with PID control. VC Series flow controllers allow the user to select how the set point is to be conveyed to the controller, what that set point is if control is local, and what the Proportional and Differential terms of the PID control loop will be. The UP and DOWN buttons for adjusting variables can be held down for higher speed adjustment or pressed repeatedly for fine adjustment. Select Loop P 2000 D 1500 Volume AUT0on Set UP DOWN Input Analog Serial Local Control Setup MODE Figure 6. VC Series Control Setup Mode Screen Input VC Series Flow Controllers normally ship defaulted to analog control as indicated in Figure 6 above. To change how the set point will be conveyed to the controller push the button in the upper right hand corner just above the dynamic label Input until the arrow is directly in front of the desired option. The controller will ignore any set point except that of the selected input and it will remember which input is selected even if the power is disconnected. Analog refers to a remote analog set point applied to Pin 4 of the Mini-DIN connector as described in the installation section of this manual. To determine what type of analog set point your controller was ordered with, refer to the Calibration Data Sheet that was included with your controller. 0-5 Vdc is standard unless ordered otherwise. Note that if nothing is connected to Pin 4, and the controller is set for analog control, the set point will float. CAUTION! NEVER LEAVE A CON- TROLLER WITH ANY NON-ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! 13

18 Serial refers to a remote digital RS-232 set point applied via a serial connection to a computer or PLC as described in the Installation and RS-232 sections of this manual. CAUTION! NEVER LEAVE A CONTROLLER WITH ANY NON-ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! Local refers to a set point applied directly at the controller. For more information on changing the set point locally refer to the heading Select below. Local input must be selected prior to attempting to change the set point locally. CAUTION! NEVER LEAVE A CONTROLLER WITH ANY NON- ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! Select To avoid accidental changing of the PID loop parameters or the set point, the Control Setup mode defaults with the selector on a null position. To change the set point or the P and D PID loop parameters, push the button in the upper left corner just above the dynamic label Select until the selection arrow is pointing to the parameter you wish to change. When the parameter you wish to change is selected, it may be adjusted up or down with the buttons under the display below the dynamic labels UP and DOWN. Press the buttons repeatedly to make slow adjustments or hold them down to make fast adjustments. P refers to the Proportional term of the PID loop. Before changing this parameter, it is good practice to write down the initial value so that it can be returned to the factory settings if necessary. D refers to the Differential term of the PID loop. Before changing this parameter, it is good practice to write down the initial value so that it can be returned to the factory settings if necessary. AUT0on / AUT0off refers to the standard auto-tare or auto-zero feature. It is recommended that the controller be left in the default auto-tare ON mode unless your specific application requires that it be turned off. The auto-tare feature automatically tares (takes the detected signal as zero) the unit when it receives a zero set point for more than two seconds. A zero set point results in the closing of the valve and a known no flow condition. This feature helps to make the device more accurate by periodically removing any cumulative errors associated with drift. Set refers to the Set Point. This parameter may only be changed if Local is selected as the Input. See above for information on selecting the input. Using the UP and DOWN buttons, the set point may be adjusted between zero and the full-scale range of the controller. CAUTION! NEVER LEAVE A CONTROLLER WITH ANY NON-ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! 14

19 Gas Select Mode The gas select mode is accessed by pressing the button labeled MODE until the dynamic label over the button reads Gas as shown in Figure 7 below. The selected gas is displayed on the default main mode screen as shown in Figure 4, and is indicated by the arrow in the gas select mode screen in Figure 7. To change the selected gas, use the buttons under the dynamic labels UP and DOWN to position the arrow in front of the desired gas. When the mode is cycled back to the main mode, the selected gas will be displayed on the main screen. In order to get an accurate volumetric flow rate, the gas being measured must be selected. This is important because the device calculates the flow rate based on the viscosity of the gas at the measured temperature. If the gas being measured is not what is selected, an incorrect value for the viscosity of the gas will be used in the calculation of flow, and the resulting output will be inaccurate in direct proportion to the difference in the two gases viscosities. (See the Volumetric and Mass Gas Flow Information section for more information.) Air Argon Methane CO CO2 Ethane H2 UP DOWN Helium N2 N2O Neon Oxygen Propane Butane Gas Figure 7. Gas Select Mode The selected gas is displayed on the default main mode screen as shown in Figure 4, and is indicated by the arrow in the gas select mode screen in Figure 7. To change the selected gas, use the buttons under the dynamic labels UP and DOWN to position the arrow in front of the desired gas. When the mode is cycled back to the main mode, the selected gas will be displayed on the main screen. Identity Mode MODE The Identity Mode is accessed by pressing the MODE button until the dynamic label over the MODE button reads I.D. as shown in Figure 8. The identity mode displays important information about your Flow Controller including the model number, serial number, and date of manufacture. Alic at S ci entific Inc. Ph Fax Model V -100CCM -D Serial No Date Mfg. 11/07/2000 Calibrated By DL Software I.D. MODE Figure 8. Identity Mode 15

20 Volumetric Flow Meters Under Pressure V and VC Series Volumetric Flow Meters and Controllers are intended for use in low pressure applications. This is because an accurate measurement of the volumetric flow rate by means of differential pressure requires the flow at the differential pressure sensor to be in a laminar state. The state of the flow is quantified by what is known as the Reynolds Number. If the Reynolds Number gets above a certain point, generally accepted as approximately 2000, the flow will become non-laminar. The Reynolds Number for a given Newtonian fluid flow is defined as: Re = ρvl/µ Where: ρ = density V = average velocity L = Constant determined by length and geometry of passage µ = viscosity From this relationship we see that increasing the gas density or velocity increases the Reynolds Number, and increasing the gas viscosity decreases the Reynolds number. For a given gas in a given meter at a given temperature, L and µ are roughly fixed constants. For the purpose of illustration, let us put two 100 (S)LPM flow meters, identical in every way except that one is a volumetric flow meter and one is a mass flow meter, in series with one another in a pipeline. Now let us pass a small constant air flow through the meters, thus fixing the velocity V though both meters. With the flow fixed, let us begin increasing the pressure, and thus the density ρ. The mass flow meter, which is measuring the absolute pressure and compensating for the density change registers this pressure increase as an increase in mass flow rate because the number of molecules of gas keeps going up in the fixed volume of flow. In addition, the Reynolds number has increased proportionately with the pressure increase because the density goes up with the pressure. If you increase the pressure high enough, the mass flow meter will max out at 100 SLPM, the Reynolds number has increased fairly dramatically, and the volumetric meter still registers your small fixed flow rate. Now if we maintain the higher pressure and try to take the volumetric meter up to its published full scale flow of 100 LPM, our density ρ AND our velocity V will be high, which often results in a high Reynolds number and non-laminar flow. When the flow is non-laminar, the Poiseuille Equation upon which we base our volumetric flow measurement is no longer valid and the meter reading is therefore no longer valid. Gas properties also need to be taken into account in deciding whether you can use a volumetric flow meter at a particular line pressure. Helium, which has a relatively low density and a relatively high viscosity at standard conditions, can generally get away with higher pressures in a volumetric flow meter. Propane, on the other hand, has a relatively high density and relatively low viscosity making it a considerably more difficult gas to measure at higher pressures in a volumetric flow meter. In air, most volumetric meters make valid full scale measurements up to PSIG line pressure. 16

21 MC Series Mass Flow Controller Operation The MC Series Mass Flow Controller is designed to provide a multitude of useful flow data in one simple, rugged device. The membrane switch user interface and dynamically labeled graphic display combine to provide exceedingly flexible and user-friendly operation. The MC Series has several screen modes. It is designed to provide maximum versatility in a compact, user-friendly mass flow controller. Main Mode The main mode screen defaults on power up with the mass flow on the primary display. The following parameters are displayed in the main mode as shown in Figure 9. PSIA C Volume Mass Set Pt SCCM Air Main MODE Figure 9. Main Mode Display, MC Series Flow Controller MODE - The MODE button in the lower right hand corner toggles the display between modes. Set Pt The set point is shown in the upper right corner of the display. The set point cannot be adjusted from the main mode screen. For information on changing the set point, see the Control Set Up Mode below. Gas Absolute Pressure: The MC Series Flow Controllers utilize an absolute pressure sensor to measure the line pressure of the gas flow being monitored. This sensor references hard vacuum and accurately reads line pressure both above and below local atmospheric pressure. This parameter is located in the upper left corner of the display under the dynamic label PSIA. This parameter can be moved to the primary display by pushing the button just above the dynamic label (top left). The engineering unit associated with absolute pressure is pounds per square inch absolute (PSIA). This can be converted to gage pressure (psig = the reading obtained by a pressure gauge that reads zero at atmospheric pressure) by simply subtracting local atmospheric pressure from the absolute pressure reading: PSIG = PSIA (Local Atmospheric Pressure) The flow controllers use the absolute pressure of the gas in the calculation of the mass flow rate. For working in metric units, note that 1 PSI = 6.89 kpa. Gas Temperature: The MC Series Flow Controllers also utilize a temperature sensor to measure 17

22 the line temperature of the gas flow being monitored. The temperature is displayed in engineering units of degrees Celsius ( C). The flow controllers use the temperature of the gas in the calculation of the mass flow rate. This parameter is located in the upper middle portion of the display under the dynamic label C. This parameter can be moved to the primary display by pushing the button above the dynamic label (top center). Volumetric Flow Rate: The volumetric flow rate is determined using the Flow Measurement Operating Principle described elsewhere in this manual. This parameter is located in the lower left corner of the display over the dynamic label Volume. This parameter can be moved to the primary display by pushing the button below the dynamic label (lower left). In order to get an accurate volumetric flow rate, the gas being measured must be selected (see Gas Select Mode page 13). This is important because the device calculates the flow rate based on the viscosity of the gas at the measured temperature. If the gas being measured is not what is selected, an incorrect value for the viscosity of the gas will be used in the calculation of flow, and the resulting output will be inaccurate in direct proportion to the difference in the two gases viscosities. Mass Flow Rate: The mass flow rate is the volumetric flow rate corrected to a standard temperature and pressure ( psia and 25 C). This parameter is located in the lower middle portion of the display over the dynamic label Mass. This parameter can be moved to the primary display by pushing the button located below the dynamic label (bottom center). The meter uses the measured temperature and the measured absolute pressure to calculate what the flow rate would be if the gas pressure was at 1 atmosphere and the gas temperature was 25 C. This allows a solid reference point for comparing one flow to another. Control Setup Mode The Control Setup Mode is accessed by pressing the button labeled MODE until the dynamic label over the button reads Control Setup as shown in Figure 10 below. This mode allows the user to set up most parameters commonly associated with PID control. Alicat Scientific flow controllers allow the user to select how the set point is to be conveyed to the controller, what that set point is if control is local, and what the Proportional and Differential terms of the PID control loop will be. The UP and DOWN buttons for adjusting variables can be held down for higher speed adjustment or pressed repeatedly for fine adjustment. Input Alicat Scientific Flow Controllers normally ship defaulted to analog control as indicated in Figure 10 above. To change how the set point will be conveyed to the controller push the button in the upper right hand corner just above the dynamic label Input until the arrow is directly in front of the desired option. The controller will ignore any set point except that of the selected input and it will remember which input is selected even if the power is disconnected. Analog refers to a remote analog set point applied to Pin 4 of the Mini-DIN connector as described in the installation section of this manual. To determine what type of analog set point your controller was ordered with, refer to the Calibration Data Sheet that was included with your controller. 0-5 Vdc is standard unless ordered otherwise. Note that if nothing is connected to Pin 4, and the controller is set for analog control, the set point will float. CAUTION! NEVER LEAVE A CONTROL- LER WITH ANY NON-ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! Serial refers to a remote digital RS-232 set point applied via a serial connection to a computer or 18

23 PLC as described in the Installation and RS-232 sections of this manual. CAUTION! NEVER LEAVE A CONTROLLER WITH ANY NON-ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! Figure 10. MC Series Control Setup Mode Screen Select Loop P 2000 Mass D 1500 Volume AUT0on Press. Set UP DOWN Input Analog Serial Local Control Setup MODE Loop The selection of what variable to close the loop on is a feature unique to these mass flow controllers. When the mass flow controller is supplied with the control valve upstream of the electronics portion of the system, the unit can be set to control on outlet pressure (absolute pressures only) or volumetric flow rate, in stead of mass flow rate. Repeatedly pressing the button adjacent to the word Loop on the control setup screen will change what variable is controlled. The change from mass to volume can usually be accomplished without much, if any, change in the P and D settings. When you change from controlling flow to controlling pressure, sometimes fairly radical changes must be made to these variables. Consult the factory if you are having difficulties with this procedure. Select To avoid accidental changing of the PID loop parameters or the set point, the Control Setup mode defaults with the selector on a null position. To change the set point or the P and D PID loop parameters, push the button in the upper left corner just above the dynamic label Select until the selection arrow is pointing to the parameter you wish to change. When the parameter you wish to change is selected, it may be adjusted up or down with the buttons under the display below the dynamic labels UP and DOWN. Press the buttons repeatedly to make slow adjustments or hold them down to make fast adjustments. P refers to the Proportional term of the PID loop. Before changing this parameter, it is good practice to write down the initial value so that it can be returned to the factory settings if necessary. D refers to the Differential term of the PID loop. Before changing this parameter, it is good practice to write down the initial value so that it can be returned to the factory settings if necessary. AUT0on / AUT0off refers to the standard auto-tare or auto-zero feature. It is recommended that 19

24 the controller be left in the default auto-tare ON mode unless your specific application requires that it be turned off. The auto-tare feature automatically tares (takes the detected signal as zero) the unit when it receives a zero set point for more than two seconds. A zero set point results in the closing of the valve and a known no flow condition. This feature helps to make the device more accurate by periodically removing any cumulative errors associated with drift. Set refers to the Set Point. This parameter may only be changed if Local is selected as the Input. See above for information on selecting the input. Using the UP and DOWN buttons, the set point may be adjusted between zero and the full-scale range of the controller. CAUTION! NEVER LEAVE A CONTROLLER WITH ANY NON-ZERO SET POINT IF NO PRESSURE IS AVAILABLE TO MAKE FLOW. THE CONTROLLER WILL APPLY FULL POWER TO THE VALVE IN AN ATTEMPT TO REACH THE SET POINT. WHEN THERE IS NO FLOW, THIS CAN MAKE THE VALVE VERY HOT! Gas Select Mode The gas select mode is accessed by pressing the button labeled MODE until the dynamic label over the button reads Gas as shown in Figure 7. The selected gas is displayed on the default main mode screen as shown in Figure 9, and is indicated by the arrow in the gas select mode screen in Figure 7. To change the selected gas, use the buttons under the dynamic labels UP and DOWN to position the arrow in front of the desired gas. When the mode is cycled back to the main mode, the selected gas will be displayed on the main screen. In order to get an accurate volumetric flow rate, the gas being measured must be selected. This is important because the device calculates the flow rate based on the viscosity of the gas at the measured temperature. If the gas being measured is not what is selected, an incorrect value for the viscosity of the gas will be used in the calculation of flow, and the resulting output will be inaccurate in direct proportion to the difference in the two gases viscosities. (See the Volumetric and Mass Gas Flow Information section for more information.) Identity Mode The Identity Mode is accessed by pressing the MODE button until the dynamic label over the MODE button reads I.D. as shown in Figure 8. The identity mode displays important information about your Flow Controller including the model number, serial number, and date of manufacture. 20

25 Configuring HyperTerminal : RS-232 Input and Output 1. Open your HyperTerminal RS-232 terminal program (installed under the Accessories menu on all Microsoft Windows operating systems). 2. Select Properties from the file menu. Make sure the com port you are connected to is selected in the connect using field. 3. Click on the Configure button under the Connect To tab. Be sure the program is set for: 19,200 baud and an 8-N-1-None (8 Data Bits, No Parity, 1 Stop Bit, and no Flow Control) protocol. 4. Under the Settings tab, make sure the Terminal Emulation is set to ANSI. 5. Click on the ASCII Setup button and be sure the Send Line Ends with Line Feeds box is not checked, the Echo Typed Characters Locally box is checked and that the Append Line Feeds to Incoming Lines box is checked. Those settings not mentioned here are normally okay in the default position. 6. If the controller is connected to the correct serial port on the computer, data should begin streaming to the window. If not, try hitting the Enter key several times to clear any extraneous information. Type *@=@ followed by Enter. If data still does not appear, check all the connections and com port assignments. Data Format: The data stream on the screen represents the flow parameters of the main mode in the units shown on the display. For volumetric flow controllers, there are two columns of data representing volumetric flow rate in the units specified at time of order and the selected gas Air Air Air Air Air Air VC Series Volumetric Flow Controller Data Format For mass flow controllers, there are 5 columns of data representing pressure, temperature, volumetric flow, mass flow and the selected gas. The first column is absolute pressure (normally in PSIA), the second column is temperature (normally in C), the third column is volumetric flow rate (in the units specified at time of order and shown on the display), and the fourth column is mass flow (also in the units specified at time of order and shown on the display). For instance, if the meter was ordered in units of SCFM, the display on the meter would read SCFM and the last two columns of the output below would represent volumetric flow and mass flow in CFM and SCFM respectively Air Air Air Air Air Air MC Series Mass Flow Controller Data Format 21

26 Sending a Set Point via RS-232: To send a set point via RS-232, Serial must be selected under the Input list in the control set up mode. To give controllers a set point, or change an existing point, simply type in a number between 0 and (2% over range), where denotes fullscale flow rate, and hit Enter. The set point column and flow rates should change accordingly. If they do not, try hitting Enter a couple of times and repeating your command. The formula for performing a linear interpolation is as follows: Value = (Desired Set Point X 64000) / Full Scale Flow Range For example, if your device is a 100 SLPM full-scale unit and you wish to apply a set point of 35 SLPM you would enter the following value: = (35 SLPM X 64000) / 100 SLPM If the controller is in polling mode as described in Changing from Streaming Mode to Polling Mode, the set point must be preceded by the address of the controller. For example, if your controller has been given an address of D, the set point above would be sent by typing: D22400 followed by Enter To adjust the Proportional and Differential (P&D) terms via RS-232: Type *@=A followed by Enter to stop the streaming mode of information. To adjust the P or proportional term of the PID controller, type *R21 followed by Enter. The computer will respond by reading the current value for register 21 between It is good practice to write this value down so you can return to the factory settings if necessary. Enter the value you wish to try by writing the new value to register 21. For example, if you wished to try a D term of 220, you would type *W21=220 followed by Enter where the bold number denotes the new value. The computer will respond to the new value by confirming that 21=220. To see the effect of the change you may now poll the unit by typing A followed by Enter. This does an instantaneous poll and returns the values once. You may type A Enter as many times as you like. Alternately you could resume streaming mode by typing *@=@ followed by Enter. Repeat step 3 to remove the unit from the streaming mode. To adjust the D or proportional term of the PID controller, type *R22 followed by Enter. The computer will respond by reading the current value for register 22 between It is good practice to write this value down so you can return to the factory settings if necessary. Enter the value you wish to try by writing the new value to register 22. For example, if you wished to try a P term of 25, you would type *W22=25 followed by Enter where the bold number denotes the new value. The computer will respond to the new value by confirming that 22=25. To see the effect of the change you may now poll the unit by typing A followed by Enter. This does an instantaneous poll and returns the values once. You may type A Enter as many times as you like. Alternately you could resume streaming mode by typing *@=@ followed by Enter. Repeat When you have decided on P and or D terms that you want, and written them to registers 21 and 22, return the unit to streaming mode (type *@=@ followed by Enter ). 22