CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin

Transcription

1 Electronic Control Manual 216 Sensors and Stats Section S Technical Bulletin CDS-2000 Issue Date 0393 CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin Introduction 3 Pre-Verification Information 3 Verification 5 Equipment Needed 5 Procedure 6 Calibration 7 Single-Point Calibration 7 Full Calibration 9 Troubleshooting 11 Maintenance and Repair 12 Recommended Maintenance 12 Servicing the Sensor 12 Accessory and Replacement Data Johnson Controls, Inc. 1 Part No Rev.

2 2 S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin

3 Introduction When properly installed, the CDS-2000 is accurate to ±100 ppm per year. The calibration should be verified after the sensor has been in operation for one full year and annually thereafter. Whenever an accuracy problem is detected via the verification procedure, the sensor should be recalibrated. Pre-Verification Information Before beginning the verification procedure, note the following: The CDS-2000 should be allowed to warm-up for at least one hour before checking calibration or before calibrating. This will ensure that the infrared sensor has reached an equilibrium temperature thereby delivering maximum calibration accuracy. Recalibration of the device should not be attempted until after 14 days of operation as the output may not have stabilized due to the drift compensation algorithm. This variation should not be confused with drift it is the self-tuning of the algorithm. The microprocessor-based compensation algorithm is based on the average of readings taken during a 30 minute or more unoccupied period (less than 500 ppm) once every 24 hours during the previous 14 days. Readings are taken and stored in non-volatile memory. If the power is removed, the readings will be retained. If after 14 days of operation the CDS-2000 appears to need recalibration, obtain a CDS Calibration Kit, and perform the single-point calibration procedure. S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin 3

4 Modes The CDS-2000 has four modes of operation: Warm-Up Primary Alarm Threshold Adjustment Calibration Notes: If it is ever unclear what mode the sensor is in during an adjustment procedure, refer to the Troubleshooting section of this bulletin. Pushbuttons SW-1 and SW-2, which are used to switch between operating modes, are recessed (Figure 1) on the front of the unit. The pushbuttons can be accessed with a small, non-metallic probe. (A metallic probe could short-circuit the unit.) When SW-1 or SW-2 is pressed, the green LED gives three quick flashes and a momentary dark pause to indicate a mode change. 4 S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin

5 Verification Before verifying or calibrating the CDS-2000, make sure that the silicone blanket and metal clips are installed. With the duct-mounted unit (CDS ), the blanket and clips should already be in place. To install the silicone blanket: remove the sensor guard and wrap the blanket around the sensor. Line up the blanket s rubber dimples with the holes on the sensing chamber and press down firmly. Fasten the blanket in place with the metal clips provided. Refer to Figure 1 for proper placement of the blanket on the sensor. Zero Adjustment SW-1 SW-2 Silicone Blanket Regulator with Gage Wiring Access Mounting Clips Green LED Tubing Adapter Alarm Threshold Adjustment 1/4 in. ID Tubing verify.drw Figure 1: Verifying Operation of the CDS-2000 Equipment Needed a digital voltmeter with 10 mvdc resolution over a range of at least 0 to 10 VDC the CDS Calibration Kit which includes: a source of air with a known concentration of CO2 between 400 and 1200 ppm (bottled gas) a regulator with gage (see Figure 1) that can maintain flow at 400 to 800 ml/min. (24 to 48 SCIM) silicone blanket with mounting clips, tubing adapter, and tubing S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin 5

6 Procedure 1. Disconnect the source of power to the CDS Connect a Digital Voltmeter (DVM) between Terminals 1 (-) and 2 (+) at the terminal block on the back of the CDS-2000, and power-up the unit. 3. Allow the CDS-2000 approximately one hour to warm-up. In the first few minutes of the warm-up, the green LED on the front of the unit below the sensor will remain dark. After a few minutes the green LED will flash continuously, which indicates that the unit is in the Primary mode. The unit will be ready for verification once the one-hour warm-up period is over. (The green LED will still be flashing.) While the unit is warming up, check the CO2 concentration of the bottled gas, (from its label) and determine the corresponding voltage level by dividing the ppm value by 200. Example: A 1000 ppm CO2 concentration corresponds to 5 VDC (1000/200). 4. Attach the regulator to the gas bottle, and connect tubing to the regulator outlet. Attach the other end of the tubing to the tubing adapter, and firmly place it into the port extending from the blanket as shown in Figure 1. With the CDS-2000 in the Primary mode, slowly adjust the regulator to flow air from the gas bottle through the tubing and into the sensor. The regulator in the Calibration Kit will deliver 500 ml/min. of gas at 10 PSI. The tank can maintain this flow for two minutes.! CAUTION: To avoid depleting the gas, slowly open the regulator valve. Close the valve as soon as verification is complete. 5. Compare the voltage reading on the DVM to the value determined in Step 3. If the two voltage levels differ by more than ±0.5 volts, proceed to the single-point calibration instructions that follow. 6. Reconnect the flow pickup device if using the duct-mounted CDS sensor. Remove the silicone blanket and metal clips if using the CDS S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin

7 Calibration The Calibration mode has two sub-modes: the Single-Point mode, which is only for adjustment of the offset, and the Full Calibration mode, which is for adjustment of the span and offset. The Calibration modes cannot be used to verify settings. To verify the settings, refer to the Verification section. If the alarm threshold needs verification, refer to the Adjusting the Alarm Threshold section in the CDS-2000 Series Carbon Dioxide Sensors Technical Bulletin. Always use the verification procedure in this bulletin to check operation before calibrating the sensor. Single-Point Calibration Equipment Needed Procedure a digital voltmeter with 10 mvdc resolution over a range of at least 0 to 10 VDC a small (0.07 in. or less), flat-blade jeweler s screwdriver a non-metallic probe for accessing the pushbuttons the CDS Calibration Kit, which includes: a source of air with a known concentration of CO2 between 400 and 1200 ppm a regulator that can maintain flow between 400 to 800 ml/min. (24 to 48 SCIM) a calibration blanket with mounting clips, adapter, and tubing To do a single-point calibration, perform the following steps: 1. Disconnect the power supply to the unit. Connect a Digital Voltmeter (DVM) between Terminal 2 (-) and Terminal 1 (+) at the terminal block on the back of the CDS-2000, and power up the unit. 2. Allow the CDS-2000 approximately one hour to warm-up. In the first few minutes of the warm-up, the green LED on the front of the unit below the sensor will remain dark. After a few minutes, the green LED will flash continuously, which indicates that the unit is in the Primary mode. The unit will be ready for calibration once the one-hour, warm-up period is over. (The green LED will still be flashing.) 3. Using a non-metallic probe, press and hold down the recessed SW-1 button, until the green LED gives three quick flashes and goes dark; then, immediately release the button. The sensor is now in the Calibration mode, and the LED remains off. S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin 7

8 4. Press and hold down SW-1 again until the LED gives three quick flashes; then, immediately release the button to switch the unit into the Single-Point Calibration mode. The voltage reading on the DVM will indicate approximately 2 VDC (400 ppm), and the LED remains off.! CAUTION: If the SW-2 button is accidentally pressed at this point, the span setting is permanently erased, and the sensor must be recalibrated using the Full Calibration Mode procedure and bottled gas at 2000 ppm of CO2. 5. Check the CO2 concentration of the bottled gas, and determine the corresponding voltage by dividing the ppm value by 200. (For example, a 1000 ppm CO2 concentration corresponds to 5 VDC (1000/200). Press SW-1 until reading at the DVM corresponds with the value calculated. Note: Repeatedly pressing SW-1 increases the voltage in 0.1 VDC (20 ppm) increments up to 6 VDC (1200 ppm). Continuously holding down SW-1 causes the voltage to increment from 2 to 6 VDC in cycles. If SW-1 is held long enough, the voltage will increment back to 0, and so on. 6. Use tubing to connect the bottled gas to the CDS-2000 as shown in Figure 11. (Refer to the instructions in the Verification Procedure section as needed.) 7. Press SW-2, and slowly adjust the regulator valve (pressure gage at 10 PSI) to flow gas into the sensor. Continue the gas flow until a stable reading is reached at the DVM. The gas will flow at 500 ml/min. for about 2 minutes with the regulator at 10 PSI. 8. When a stable reading is achieved (not necessarily the calculated voltage), press SW-1 to return the unit to the Primary mode. The LED now flashes continuously indicating that the CDS-2000 has resumed operation using the new settings. The reading at the DVM should be the same value (within ±0.1 volts) as that calculated in Step Disconnect the DVM. Reconnect the flow pickup device if using the CDS Remove the silicone blanket and metal clips if using the CDS S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin

9 Full Calibration Equipment Needed Procedure a digital voltmeter with 10 mvdc resolution and a range of at least 0 to 10 VDC a small (0.07 in. or less), flat-blade jeweler s screwdriver a small, non-metallic probe for accessing the pushbuttons a source of dry nitrogen gas from which all CO2 has been removed (0 ppm) a source of air with a known concentration of 2000 ppm (±40 ppm) CO2 a regulator that can maintain flow between 400 and 800 ml/min. (24 to 48 SCIM) a silicone blanket and tubing Use the following procedure only when it is necessary to completely reset the sensor s offset and span.! CAUTION: Make sure bottled gas at 2000 ppm CO2 and a bottle at 0 ppm CO2 concentration is available before beginning calibration. The previous span setting is automatically erased when the Full Calibration Mode procedure is initiated. 1. Connect the Digital Voltmeter (DVM) between Terminal 8 (+) and Terminal 2 (-) on the terminal block (back of the unit). Power up the unit. 2. Allow the CDS-2000 approximately one hour to warm-up. In the first few minutes of the warm-up, the green LED on the front of the unit below the sensor will remain dark. After a few minutes, the green LED will flash continuously, which indicates that the unit is in the Primary mode. The unit will be ready for verification once the onehour warm-up period is over. (The green LED will still be flashing.) 3. Using a non-metallic probe, press and hold down the recessed SW-1 button until the green LED gives three quick flashes and goes dark; then, immediately release the button. The unit is now in the Calibration mode, and the LED remains off. 4. Press and hold down the SW-2 button (to the right of SW-1, see Figure 1) until the LED gives three quick flashes and a momentary dark pause; then, immediately release the button to switch the unit into the Full Calibration mode (LED will be flashing continuously). S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin 9

10 5. Use tubing to connect the 0 ppm gas to the CDS-2000 s tubing port shown in Figure 1. (Refer to the instructions in the Verification Procedure section as needed.) Slowly adjust the regulator valve to flow gas into the sensor. Continue flowing the gas until a stable reading is reached at the DVM. (This will take about 2 minutes at 500 ml/min.) When a stable reading is achieved at the DVM, use the small-blade screwdriver to slowly adjust the recessed zero adjustment potentiometer (to the left of SW-1, see Figure 1) until the DVM reads between 2.75 and 2.85 VDC. Turn Clockwise (CW) to decrease or Counterclockwise (CCW) to increase. Note: A 0.2 V, 1 Hz signal is superimposed on the DC level. The 2.8 VDC value should correspond with the highest of the two values, which alternate on the DVM readout. 6. Press the SW-1 button until the LED gives three quick flashes and a momentary dark pause (the LED will then flash continuously). Release the button, and flow 2000 ppm CO 2 gas into the sensor until a stable reading is reached (between 0.4 and 0.8 volts). 7. When a stable reading is achieved (will take about 2 to 3 minutes), press the SW-1 button to return the unit to the Primary mode (LED flashes continuously). If the 8 (+) lead of the DVM is moved to Terminal 1 at this point, the DVM should read between 9.5 and 10.5 VDC. (If not, refer to the Troubleshooting section.) Disconnect the DVM. 8. Reconnect the flow pickup device if using the CDS Remove the silicone blanket and metal clips if using the CDS S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin

11 Troubleshooting If the SW-1 and SW-2 buttons are tampered with or are pressed out of sequence during an adjustment or calibration procedure, the CDS-2000 may not operate properly. The flowchart below and the green LED can be used to determine what status/mode the CDS-2000 is in and how to return to the Primary mode. Use it if there is ever any confusion about what mode the sensor is in or to recover from an unsuccessful calibration attempt. IMPORTANT: Once the Single-Point or Full Calibration modes are selected, all previous calibration settings are erased. PRESS SW-2 LED Gives 3 Quick Flashes, Then Stays Dark PRIMARY MODE LED Flashes Continuously PRESS SW-1 Then Stays Dark ALARM THRESHOLD ADJUSTMENT MODE Adjust Threshold Potentiometer to Desired Setting Press SW-2 to Store Desired Setting * Do NOT proceed from this point unless the appropriate supply of bottled gas at the indicated CO 2 concentration is available. Once the Full Calibration Mode Procedure is initiated, the procedure must be completed. SINGLE POINT CALIBRATION Press SW-1 to Select Output Voltage PRESS SW-1 CALIBRATION SELECT MODE Then Stays Dark Press SW-2 After Voltage Selection Flow Gas Press SW-1 After Reading Stabilizes PRESS SW-2 * FULL CALIBRATION Flow 0 ppm Gas and Adjust Zero Potentiometer Press SW-1 Flow 2000 ppm Gas Press SW-1 cdsflow.drw Figure 2: Troubleshooting Guide S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin 11

12 Maintenance and Repair Recommended Maintenance Servicing the Sensor Accessory and Replacement Data To ensure maximum performance from the CDS-2000: keep the air vents on the unit clean and unobstructed verify sensor calibration annually. If necessary, recalibrate as indicated in the Calibration section of this bulletin to prevent inaccuracy due to drift. If the CDS-2000 fails verification and subsequent field adjustment of the calibration settings does not correct the problem, contact your local Johnson Controls branch or distributor office. Note: The CDS-2000 cannot be repaired in the field. Contact your local Johnson Controls representative to arrange for a unit replacement. If a replacement unit is required, specify the complete product code number from Table 1, and contact the nearest Johnson Controls branch office or wholesale distributor. A Single-Point Calibration Kit for the CDS-2000 can also be ordered using Table 1. Table 1: CDS-2000 Ordering Information PRODUCT CODE NUMBER PRODUCT CDS Duct-Mount CO 2 Sensor CDS Wall-Mount CO 2 Sensor CDS Single-Point Calibration Kit DESCRIPTION With round base, ppm CO 2 range, 0-10 VDC output and SPST/NO alarm relay With telephone-style base, ppm CO 2 range, 0-10 VDC output and SPST/NO alarm relay For verification and single-point calibration of CDS-2000 Series Carbon Dioxide Sensors A Air Filter Use with the CDS in duct applications where the flow pickup tube is installed Controls Group FAN E. Michigan Street Electronic Control Manual P.O. Box 423 Issue Date 0393 Milwaukee, WI Printed in USA 12 S Sensors and Stats CDS-2000 CO 2 Sensor Verification, Calibration, and Troubleshooting Bulletin