operating Instructions

Transcription

1 4 Function IAQ Probes operating Instructions 1260GSS IAQ Surveyor Probe GrayWolf Sensing Solutions advanced environmental measurements

2 HELP US TO HELP YOU Every effort has been made to ensure the accuracy in the contents of our documents, however, GrayWolf Sensing Solutions can assume no responsibility for any errors or omissions in our documents or their consequences. GrayWolf would greatly appreciate being informed of any errors or omissions that may be found in the contents of any of our documents and to this end we include the following form for you to photocopy, complete and return to us so that we may take the appropriate action. 2

3 HELP US TO HELP YOU To: From : Address : GrayWolf Sensing Solutions 12 Cambridge Dr. Trumbull, CT Phone: Fax: sales@wolfsense.com Tel : Fax : I suggest the following corrections/changes be made to Section... Marked up copies attached (as appropriate): Yes / No Please inform me of the outcome of this change: Yes / No For Marketing Communications, GrayWolf: Actioned By: Response: Date: Date: 3

4 CONTENTS 1. ABOUT THE FOUR FUNCTION IAQ PROBE General Description Probe Specification Sensor Types Range, Resolution and Accuracy % Response Times Environmental Dimensions and Weight Housing IAQ Surveyor Interface Probe Accessories USING THE SMART FOUR FUNCTION PROBE Introduction Operational Use and Storage Instrument Connections Monitoring IAQ Parameters CALIBRATING THE PROBE Introduction Test Equipment and Materials General CA-GCK4-CL Gas Calibration Kit CA-HC4-CL Calibration Kit Calibrating the Gas Sensors 18 4

5 CONTENTS Calibration Intervals Preparing to Calibrate a Gas Sensor Carbon Dioxide Calibration Carbon Monoxide Calibration Calibrating the % rh Sensor Calibration Intervals Calibration Preparation Preparing the Zero Reference Desiccant Preparing the Salt Solution Calibration Procedure MAINTENANCE Routine Maintenance Sensor Replacement General Replacing a CO Sensor 30 FIGURES 1 Smart Four Function Probe Fitted to the IAQ Surveyor 6 2 Disassembly of the Sensor Head 30 3 Disassembly of the Sensor Head 30 4 Disassembly of the Sensor Head 31 5

6 Figure GSS Smart Four Function Probe Fitted to the IAQ Surveyor Instrument 6

7 1. ABOUT THE SMART FOUR FUNCTION PROBE 1.1 GENERAL DESCRIPTION The 1260GSS Smart Four Function Probe is a hand held indoor air quality (IAQ) monitoring device designed for use with the GrayWolf IAQ Surveyor instrument (Figure 1). The probe monitors temperature and relative humidity, from which the Surveyor instrument calculates the dewpoint temperature, and the concentration levels of carbon dioxide (CO 2 ) and carbon monoxide (CO). The probe is connected to the bottom of the IAQ Surveyor by a 2 meter (6½ ft) cable terminated in an 8-pin Binder plug. Power to operate the probe is supplied by the IAQ Surveyor. A dedicated temperature sensor, fitted close to the CO 2 sensor body, is used for temperature compensation for the CO 2 sensor. Temperature compensation calculations are carried out within the IAQ Surveyor so that, in practice, a total of five sets of data are multiplexed to the IAQ Surveyor. 1.2 PROBE SPECIFICATION 7

8 1. ABOUT THE SMART FOUR FUNCTION PROBE Sensor Types Temperature: Platinum Pt100 RTD, 0.1% grade. (ambient and CO 2 compensation) Relative Humidity: Carbon Monoxide: Carbon Dioxide: Rapid response capacitive polymer. Electrochemical CO micro sensor. Infrared NDIR Optical Bench sensor Range, Resolution and Accuracy The following performance figures apply to the combination of a 1260GSS Four Function Probe and IAQ Surveyor instrument: Parameter Range Resolution Accuracy Temperature: 0 to +40 C 0.1 C ±0.5 C (See Note 1) Relative Humidity: 0 to 100% 0.1% ±2% (<75% rh) ±3% (>75% rh) Carbon Monoxide: 0 to 500ppm 0.1ppm ±2ppm (<40ppm) ±5% (>40ppm) Carbon Dioxide 100ppm to 1ppm ±5% ± 50ppm (NDIR sensor) 5000ppm 8

9 1. ABOUT THE SMART FOUR FUNCTION PROBE Notes 1. Although the IAQ Surveyor is capable of displaying a wider temperature range, the range specified is determined by the electrochemical sensor (CO) in the probe % Response Times The following T90 response times, (ie. the time taken for the displayed measurement to show 90% of the ambient condition), apply to the IAQ Surveyor and Smart Four Function Probe combination when exposed to air flow at 0.25m/s (50 ft/minute): Temperature: Relative Humidity: Carbon Monoxide: Carbon dioxide: 30 seconds. 30 seconds. 45 seconds. Less than 60 seconds Environmental Operating Range: Temperature: Humidity: 0 C to +40 C (32 F to 104 F). 0% rh to 100% rh (non condensing). Storage Range: Temperature: Humidity: 0 C to +25 C (32 F to 77 F). 0% rh to 100% rh (non condensing). 9

10 1. ABOUT THE SMART FOUR FUNCTION PROBE Dimensions and Weight Handle Length: Overall Length: Handle Diameter: Maximum diameter Weight: 135mm (5.3 inches). 260mm (10.2 inches). (Including cable strain relief). 40mm (1.6 inches). 50mm (2 inches). 350g (12 oz) (Including cable) Housing Material: Sealing: Black acetal. IP44. EMC Protection: Emission EN55022 Class B. Immunity EN

11 1. ABOUT THE SMART FOUR FUNCTION PROBE 1.3 IAQ SURVEYOR INTERFACE The IAQ Surveyor/Probe interface connections are as follows: Pin Signal Description 1 +5V Regulated power supply. 2 IN Hi rh, CO 2, CO multiplexed analog signal. 3 SCL Serial control to probe multiplexer circuits. 4 0 V Ground. 5 SDA Serial control to probe multiplexer circuits. 6-5V Regulated power supply. 7 REF Hi 2.5V reference voltage. 8 IN Lo rh, CO 2, CO multiplexed analog signal. 1.4 PROBE ACCESSORIES. Accessories and spares are available for use with the Smart Four Function Probe: a. CA-HC4-CL Relative Humidity Calibration Kit b. CA-GCK4-CL CO and CO 2 Gas Calibration Kit c. CA-1260R-CL Gas calibration ring (note: one comes with the CA-GCK4-CL Gas Calibration Kit). d. ACC-ADY125-CL Y power adapter for connecting power simultaneous to the 1260GSS (only required when 2300AHTS 3 function probe is also connected). 11

12 2. USING THE SMART FOUR FUNCTION PROBE 2.1 INTRODUCTION The 1260GSS Four Function Probe is intended for monitoring indoor air quality in conjunction with the IAQ Surveyor instrument. This section is concerned with providing user information specific to that particular probe/instrument combination and general information regarding the measurement of IAQ parameters. 2.2 OPERATIONAL USE AND STORAGE Instrument Connections Connect the probe to the 8-way socket on the bottom of the IAQ Surveyor instrument. Regulated power supplies to operate the probe are provided by the instrument when it is switched on. There are no operator controls on the probe itself Monitoring IAQ Parameters a. Temperature Indoor air quality is a function of several factors of which temperature is the most important thermal comfort measurement. Not only does it need to be controlled tightly, typically between 20 C (68 F) and 25 C (77 F), but sudden temperature changes can cause discomfort. Temperature also indirectly affects other comfort parameters such as relative humidity. 12

13 2. USING THE SMART FOUR FUNCTION PROBE By monitoring the air temperature for a week, it is possible to follow a building s air handling behavior. ie. Monitor the: a. insulation efficiency by checking the temperature after the heating is turned off. b. thermostat temperature cycling around its setpoint. c temperature set back thermostat. Where a building is being ventilated by the introduction of outdoor air, the percentage quantity of outdoor air being added to the internal supply, can be calculated by the equation: Outdoor air (%) = [(Tr - Ts) (Tr - To)] x 100 Where Ts = Supply/mixed air temperature. Tr = Return air temperature. To = Outdoor air temperature b. Relative Humidity and Dewpoint Both relative humidity (rh) and absolute humidity (dewpoint) affect micro organism growth, especially in duct systems. Most viruses grow best in low temperature/high humidity conditions. Formaldehyde emissions also increase when both relative humidity and temperature increase. In addition to the health implications for occupants, high humidity may adversely affect their perception of thermal comfort. A low % rh is not an answer to all IAQ problems since if the % rh is too low, eye irritation, skin irritation and respiratory tract problems may arise. Dust is generally more of a problem in low humidity situations. Hence, % rh limits for IAQ purposes are usually specified as being between 30% and 60%. 13

14 2. USING THE SMART FOUR FUNCTION PROBE The IAQ Surveyor uses the temperature and relative humidity data provided by the 1260GSS Four Function Probe to calculate dewpoint. In general, the dewpoint temperature should be at least 10 C (18 F) below the ambient temperature. c. Carbon Monoxide Carbon monoxide is a colorless, odorless, toxic gas. Its indoor concentration should always be very close to zero. The readings may be raised by the presence of tobacco smoke or if the outside air used for dilution is coming from a busy city center where car emissions can raise the CO level. It is important that the CO concentration is checked in IAQ audits, particularly where direct fired heat exchangers are used. Corrosion or mechanical damage to the heat exchanger causes mixing of the combustion gas with the return air, resulting in a buildup of CO inside the building. Inhalation of CO is highly toxic even at relatively low concentrations, and in high concentrations can cause immediate collapse and death. Any concentration in excess of a few ppm should always be investigated. d. Carbon Dioxide Carbon dioxide concentration level is an important parameter to measure since it can be used as an outside air dilution index in the same way as temperature. As a surrogate indicator of air quality, CO 2 is the most widely used tracer gas for measuring air dilution and ventilation. Outside air has a typical CO 2 concentration of 340ppm. Wherever people are present in a building the ambient CO 2 level however increases rapidly. This parameter provides a natural tracer through the building s ventilation system. 14

15 2. USING THE SMART FOUR FUNCTION PROBE Poor ventilation generally maintains a high CO 2 level, whereas good ventilation normally keeps the CO 2 level low. When taking measurements, it should be remembered that: a. CO 2 is heavier than air, and in the absence of mixing, the concentration is highest near the floor. b. a high CO 2 measurements in corners of a room show that the ventilation is stagnant. Where a building is being ventilated by the introduction of outdoor air, the percentage quantity of outdoor air being added to the internal supply, or mixed, can be calculated by the following equation: Outdoor air (%) = [(Cr - Cs) (Cr - Co)] x 100 Where Cs = Supply/mixed air CO 2 concentration (ppm). Cr = Return air CO 2 concentration (ppm). Co = Outdoor air CO 2 concentration (ppm). Other techniques using CO 2 as a tracer gas, (ie. tracer decay and tracer equilibrium methods), can also be useful when determining outdoor air ventilation rates. The American Society of Testing and Materials (ASTM) Provisional Standard PS40-95 provides additional information on applying CO 2 measurements to IAQ investigations. 15

16 2. USING THE SMART FOUR FUNCTION PROBE 16

17 3. CALIBRATING THE PROBE 3.1 INTRODUCTION CO, CO 2 and %RH ensors in the 1260GSS Four Function Probe require calibration either at prescribed intervals or if obviously incorrect measurements are obtained, or when used in dirty environments, including areas where the sensors are subjected to tobacco smoke. Pt100 platinum resistance temperature detectors (RTD) are mechanically and electrically stable and resistant to contamination or oxidation. The temperature sensor and the temperature compensation sensor in the probe do not require routine calibration, even in dirty environments. 3.2 TEST EQUIPMENT AND MATERIALS General The following test equipment and materials are required for end-users to calibrate the gas (CO and CO 2 ) and % rh sensors in the Smart Four Function Probe: a. The IAQ Surveyor instrument with which the probe is to be used. b. CA-GCK4-CL Gas Calibration Kit see Section c. CA-HC4-CL Relative Humidity Calibration Kit see Section d. Distilled water CA-GCK4-CL Gas Calibration Kit If the CA-GCK4-CL Gas Calibration Kit is not available, the following items are required: 17

18 3. CALIBRATING THE PROBE a. Test gases contained in cylinders that are fitted with a low flow (300 ml/minute) gas regulator: Carbon dioxide - typically ~1000ppm in air. Carbon dioxide - typically ~300ppm in air. Carbon monoxide - typically ~95ppm in air or nitrogen. b. CA-1260R-CL gas calibration ring. c. Gas tubing of suitable size and length to connect the test gas cylinder to the gas flow hood (ideally at least 2m (6½ ft) long to allow gas temperature stabilisation) CA-HC4-CL Calibration Kit If the CA-HC4-CL Calibration Kit is not available, the following items are required: a. Salt for preparing 75% rh calibration solution, typically high purity sodium chloride. b. Molecular sieve desiccant for 0% rh calibration. c. Two plain (unmodified) lids suitable for sealing the calibration jars. 3.3 CALIBRATING THE GAS SENSORS CAUTION Gas sensors (CO and CO 2 ) should be calibrated under stable ambient conditions of between 20 C and 25 C. For precise calibration of NDIR CO 2 sensors, atmospheric pressure is also important (see Section 3.3.4). 18

19 3. CALIBRATING THE PROBE Calibration Intervals It is recommended that the following calibration intervals are observed: a b The NDIR CO 2 sensor should be calibrated at six month intervals. Refer to Section The CO sensor should be calibrated at six month intervals. Refer to Section Depending on the purpose for which the probe is being used, there may be mandatory requirements for either or both of the gas sensors (CO and CO 2 ) to be calibrated at more frequent intervals than those recommended above. Many environmental professionals choose a stringent QA policy that includes calibration at the beginning of each survey, and sometimes an additional sensor calibration check at the end of the survey Preparing to Calibrate a Gas Sensor WARNING Test gases are vented to the atmosphere during the following procedures. Ensure there is adequate ventilation or use a Fume Hood or Fume Cupboard for CO gas span calibration. (1) Fit the CA-1260R-CL calibration ring to the probe. Optimally, locate it over the mid section of the sensor to be calibrated, and connect the probe to the IAQ Surveyor. The CO sensor is the ~1 cm (7/16") diameter round sensor that may be viewed through the slots on the side of the probe. The CO 2 sensor is the ~2cm x6 cm (7/8" x 2 1/2") sensor that flashes when powered. 19

20 3. CALIBRATING THE PROBE (2) Connect the gas tubing to the gas flow hood. (3) Switch on the IAQ Surveyor and allow two or three minutes until the readings to stabilize. (4) Proceed with the CO 2 and/or CO sensor calibration. A full two point (Low Cal and High Cal) calibration is recommended for all sensors. Note: Refer to the IAQ Surveyor Operating Instructions for the setting of the Low Cal and High Cal calibration points Carbon Dioxide Calibration (NDIR Sensor) CAUTION For precise measurements of CO 2 using an NDIR sensor, atmospheric pressure must be taken into account. ie. If a calibration is carried out at 1000mbar, indicated measurements made at 950mbar are 5% less than actual and those made at 1050mbar are 5% more than actual. (1) Connect the low concentration CO 2 test gas cylinder to the gas flow hood and turn on the gas. (2) With the IAQ Surveyor in the Meter mode, observe the CO 2 reading. (3) Wait approximately five minutes for the reading to stabilize and then enter the instrument Menu mode and select 20

21 3. CALIBRATING THE PROBE CO 2 Calibration. (4) Using the Do Standard Cal Setup option, check that the CO 2 Low Cal and High Cal calibration points match the concentrations certified on the test gas cylinders. If necessary, reset the calibration points on the IAQ Surveyor. (5) Proceed with the Do Standard Low Cal calibration of the CO 2 channel. (6) Turn off the test gas and disconnect the low concentration test gas cylinder. (7) Reset the IAQ Surveyor to Meter mode. (8) Connect the high concentration CO 2 test gas cylinder to the gas flow hood and turn on the gas. (9) Wait approximately five minutes for the reading to stabilize and then enter the instrument Menu mode and select CO 2 Calibration. (10) Proceed with the Do Standard High Cal calibration of the CO 2 channel. (11) Turn off the test gas and disconnect the high concentration test gas cylinder. (12) Switch off the IAQ Surveyor. (13) If no other calibrations are required, return the probe/ instrument to normal use. 21

22 3. CALIBRATING THE PROBE Carbon Monoxide Calibration A 0.5 ppm CO test gas is normally included as part of the CA- GCK4-CL Gas Calibration Kit. In the absence of a ~0 ppm CO test gas, the probe may be exposed to clean, fresh air for the purpose of the Low Cal calibration, with the concentration assumed to be 0.0ppm. (1) Connect the low concentration CO test gas cylinder to the gas flow hood and turn on the gas. (2) With the IAQ Surveyor in the Meter mode, observe the CO reading. (3) Wait approximately 2-3 minutes until the reading stabilizes and then enter the instrument Menu mode and select CO Calibration. (4) Using the Do Standard Cal Setup option, check that the CO Low Cal and High Cal calibration points match the concentrations certified on the test gas cylinders. If necessary, reset the calibration points on the IAQ Surveyor. (5) Proceed with the Do Standard Low Cal calibration of the CO channel. (6) Turn off the test gas and disconnect the low concentration test gas cylinder. (7) Reset the IAQ Surveyor to Meter mode. (8) Connect the high concentration CO test gas cylinder to the gas flow hood and turn on the gas. (9) Wait approximately 2 to 3 minutes until the reading 22

23 3. CALIBRATING THE PROBE stabilizes and then enter the instrument Menu mode and select CO Calibration. (10) Proceed with the Do Standard High Cal calibration of the CO channel. (11) Turn off the test gas and disconnect the high concentration test gas cylinder. (12) Switch off the IAQ Surveyor. (13) If no other calibrations are required, return the probe/ instrument to normal use. 23

24 3. CALIBRATING THE PROBE 3.4 CALIBRATING THE % RH SENSOR Calibration Intervals It is recommended that the % rh sensor is calibrated at 12 month intervals. In high humidity/high temperature applications, or in polluted or smoky environments, more frequent calibration is recommended (eg. at 2, 3 or 6 month intervals, depending on the severity of the conditions). Calibration of the % rh sensor comprises a full two point calibration (Low Cal and High Cal). The sensor normally retains its accuracy over long periods and the calibration measurements obtained prior to readjustment should not differ significantly from the Low Cal and High Cal settings. If they do, it may be indicative of a contaminated sensor requiring the probe to be returned to GrayWolf or one of their Service Agents for repair. Note: Reference must be made to the instructions given in the IAQ Surveyor Operating Instructions for setting the Low Cal and High Cal calibration points Calibration Preparation Calibration of the % rh sensor requires the exposure of the probe to a molecular sieve desiccant for the zero (Low Cal) setting, and to a salt solution for the span (High Cal) setting. Two calibration jar assemblies are required, containing respectively the zero reference desiccant (see Section 3.4.3) and the salt solution (see Section 3.4.4) Preparing the Zero Reference Desiccant (1) Pour a quantity of the molecular sieve desiccant into a calibration jar to such a depth that when the probe is inserted in the jar, its end is approximately 3mm (1/8 24

25 3. CALIBRATING THE PROBE inch) above the top of the desiccant. (2) Using the plain lid to seal the calibration jar. The desiccant will maintain 0% to 0.5% rh so long as the jar is well sealed. Note: The modified lid should be fitted to the jar only while the probe is being calibrated, and then replaced with the plain lid immediately afterwards. The desiccant can absorb up to 5% of its own weight before starting to lose its effectiveness which is indicated by its inability to maintain 0% rh. When this occurs, the desiccant can be rejuvenated by drying it for three hours in an oven at 250 C to 300 C (480 F to 570 F). The desiccant should then be immediately transferring to the calibration jar and the jar sealed. The desiccant should be allowed to cool in the jar Preparing the Salt Solution A salt solution to yield 75.3% rh at 25 C (77 F) is obtained by adding sodium chloride to distilled water in the proportion 200g to 56ml (7 oz to 2 fluid oz). (1) Pour 56ml of distilled water into the calibration jar and add 200g of sodium chloride while stirring with a glass or plastic rod. (2) Adjust the depth of salt solution in the calibration jar so that when the probe is inserted in the jar its end is approximately 3mm (approximately 1/8 inch) above the solution surface. 25

26 3. CALIBRATING THE PROBE The probe body must not come into contact with the salt solution. Ideally, the top 2mm (approximately 1/10 inch) of the solution should be water as this will ensure the recommended condition of a thin layer of saturated water above a salt precipitate. Excess water should be removed using a syringe. (3) Seal the calibration jar and allow the solution to stabilize for 24 hours at a constant temperature (not less than 1 C/hour variation) of between 20 C and 30 C (68 F and 86 F) before use. The following general rules apply to the use of the salt solutions for accurate % rh calibration. a. The rh provided by the salt solution varies linearly from 75.5% at 20 C (68 F) to 75.1% at 30 C (86 F). The calibration room temperature should Ideally be between 24.5 C and 25.5 C (76 F and 78 F). If the temperature is outside this range, the High Cal calibration point quoted in the following calibration procedure should be revised accordingly. b. During calibration, avoid raising the salt solution or % rh sensor temperatures beyond the optimum 25 C (77 F) by not touching the calibration jar or holding the probe body for longer than necessary. c. Always ensure that the calibration jar is sealed when the solution is not in use. The modified lid should be fitted only while the probe is being calibrated, and then replaced with the plain lid immediately afterwards. 26

27 3. CALIBRATING THE PROBE d. Before use, check that the salt solution has not given off so much water that it has become dehydrated. e The salt solution has a finite life and must be renewed at one month intervals Calibration Procedure Note: Refer to the instructions given in the IAQ Surveyor Operating Instructions for resetting the Low Cal and High Cal calibration points. While exposing the probe to the desiccant or salt solution and waiting for the reading to stabilize, check the sensor and calibration jar temperature by temporarily displaying the IAQ Surveyor temperature measurement. Ensure that this reading is within the limits of 24.5 C to 25.5 C (76 F to 78 F) while the calibration adjustments are being made. (1) Switch on the IAQ Surveyor. (2) Fit the probe into the zero reference desiccant calibration jar and connect it to the IAQ Surveyor. (3) With the IAQ Surveyor in the Meter mode, observe the % rh reading. (4) Wait 45 to 60 minutes for the measurement to stabilize and then enter the Menu mode on the instrument and select RH Calibration. (5) Using the Do Standard Cal Setup option, check that the rh Low Cal and High Cal calibration points are 0.0% and 75.3% respectively. If necessary, reset the calibration points on the IAQ Surveyor. (6) Proceed with the Do Standard Low Cal calibration of the % rh channel. 27

28 3. CALIBRATING THE PROBE (7) Remove the probe from the calibration jar and allow it to stabilize in ambient air for ten minutes. (8) Fit the probe into the salt solution calibration jar. (9) Reset the IAQ Surveyor to the Meter mode and observe the % rh measurement. (10) Wait 45 to 60 minutes for the measurement to stabilize and then enter the Menu mode on the instrument and select RH Calibration. CAUTION Do not expose the probe to the sodium chloride solution for more than 75 minutes as this may cause the % rh sensor to saturate, which is indicated by the displayed measurement increasing continuously instead of stabilizing. (11) Proceed with the Do Standard High Cal calibration of the % rh channel. (12) Remove the probe from the calibration jar and switch off the IAQ Surveyor. If no other calibration is required, return the probe/instrument to normal use. 28

29 4.1 ROUTINE MAINTENANCE Routine maintenance of the four function probe consists of periodic calibrations of the gas and relative humidity channels as described in Section 3. CO sensors have a limited lifetime and readings will become sluggish as they age. They should be replaced at intervals of not more than three years (see Section 4.3). % rh, NDIR CO 2 and temperature sensors have a life expectancy of at least three years and do not need replacing as a routine maintenance exercise. 4.2 SENSOR REPLACEMENT General 4. MAINTENANCE On probes where the CO sensor become noticeably sluggish or fails to calibrate satisfactorily the the sensor will need to be replaced. These replacements may be carried out by suitably qualified personnel, either as routine maintenance or as a corrective maintenance (repair) exercise. Alternatively, the probe can be returned to GrayWolf or one of their Service Agents for sensor and battery replacement. Note: Only the probe need be returned for repair and subsequent recalibration. It is not necessary to return the IAQ Surveyor instrument with the probe, unless an NIST, NPL or other traceable standards calibration is required for the combined probe and instrument. 29

30 4. MAINTENANCE For all other repairs, defective probes must be returned to GrayWolf or one of their Service Agents Replacing a CO Sensor CAUTION Static sensitive devices are fitted to the pcb inside the probe. Suitable antistatic precautions (ie. wearing an earthed wrist strap) should be observed during the following procedures. Take care not to touch the % rh sensor since this device is easily damaged by material contact. a. To replace a CO sensor: (1) Unscrew the probe body from the sensor housing and carefully slide it back along the cable to expose the sensors. (2) Remove the protective rubber bung from the sensor housing. (3) Remove the three M2.5 countersunk head screws securing the sensor housing, and then carefully slide the housing off the end of the probe (see Figure 2). (4) Remove the three M2.5 countersunk head screws Figure 2 Disassembly of the Sensor Head 30

31 4. MAINTENANCE securing the complete sensor and pcb assembly to the pcb support, and then carefully pull the assembly away from its 14-pin connector on the main pcb (see Figure 3). If necessary, the CO sensor can now be extracted from Figure 3 Disassembly of the Sensor Head the pcb assembly and a replacement sensor fitted. (5) Reassemble the probe in the reverse order of the above disassembly procedure and proceed with the calibration of the CO sensor (see Section 3.3). 31

32 GrayWolf Sensing Solutions 12 Cambridge Dr. Trumbull, CT Phone: Fax: GrayWolf Sensing Solutions Tuamgraney Industrial Estate Tuamgraney, Co Clare, Ireland Phone: (353) Fax: (353) DISTRIBUTOR: GrayWolf Sensing Solutions advanced environmental measurements