Carbon Dioxide Sensor AirTest Model TR-9200

TR-9200 - 4-20 mA Sensor / Transmitter

The AirTest TR-9200 is a non-dispersive infrared analyzer for measuring environmental CO2 (Carbon Dioxide) concentration in ventilation systems and indoor living spaces. measurement range of 0 - 5000 ppm covers the range required to monitor compliance with ASHRAE or other ventilation efficiency standards. The TR-9200 provides several output alternatives. A voltage or 4 - 20 mA current output is standard. An optional LCD readout is available. An optional relay contact can be configured to open or close above a user-adjustable setpoint. A simple one-point calibration procedure and a built-in calibration port that requires no special fittings or adapters make the TR-9200 simple to maintain.

Specifications  |  Installation  |  Calibration  |  Duct Sampling Option  |  Limited Warranty and Remedies  |  Dimensions  |  Wire Diagrams

Installation

Cover Removal 

To open the TR-9200 use a coin in the slot on the bottom to release the snap. Lift the cover up slightly to disengage the closure and remove cover with a downward motion to clear the catch at the top of the unit. The locations of controls and terminals on the main circuit board are shown in Figure 2.

Mounting 

The TR-9200 is designed for flush mounting with two fasteners. The locations of the mounting points (shown in Figure 1) allow direct mounting on a standard simplex (single circuit) junction box. There is a wiring cutout in the center of the unit near the terminal strips.

Figure 1

Wiring

This section describes the external connections to the TR-9200. Wiring enters the chassis through the cutout in the center of the unit.

Figure 2

Power Supply

The TR-9200 will operate from an AC or DC input voltage between the values called out in the specifications. The power supply leads are connected to the two-terminal power connector shown in Figure 2. The TR-9200 must never be connected directly to line power. Operation at voltages higher than specified will damage the unit and void the warranty. When operating from DC power, the polarity of the power leads must be as shown in Figure 2. Reversed polarity connection will not damage the unit, but will make it inoperable until the connection is reversed.

Signal Output

The TR-9200 provides either a 0 - 10 volt or a 4 - 20 mA current loop output at the two terminals of the analog output connector shown in Figure 2. The type of analog output is determined by the setting of the analog output selector shown in Figure 2. The analog output of the TR-9200 is completely isolated from the power supply. The common outputs of multiple units can be connected together with no interaction regardless of power supply hook-up.

Voltage

When the outboard and middle pins of the analog output selector are connected with the shorting block, a voltage output appears between the two terminals marked ANALOG OUTPUT. The output voltage increases linearly from 0 volts at the low output threshold to 10 volts at the high output threshold. The unit is shipped from the factory with the low output threshold at 0 ppm and the high output threshold at 2000 ppm. See the Analog Output Range Adjustment section to change the analog output range limits.

Current

When the inboard and middle pins of the analog output selector are connected with the shorting block, a current output appears between the two terminals marked ANALOG OUTPUT. The output current increases linearly from 4 mA at the low output threshold to 20 mA at the high output threshold. The unit is shipped from the factory with the low output threshold at 0 ppm and the high output threshold at 2000 ppm. See the Analog Output Range Adjustment section to change the analog output range limits. If the total resistance between the two terminals exceeds the specified maximum loop resistance, the output current may be erroneously low at high concentrations.

Verifying Voltage or Current Output Connection

After the voltage or current output of the TR-9200 is connected to a controller or indicator, the following check should be performed to ensure that the connection has been properly established and the TR-9200 is transmitting the correct values:

1. Be sure that the output select jumper is set correctly for voltage or current output. If this is not done first, the following check may produce incorrect results. Note whether the shorting block at jumper JP5 is covering both pins or only a single pin, then borrow the shorting block and slide it over the two pins of jumper JP4 (see Figure 2). The display (if present) will show 'SEL'. Be sure to remove the jumper from JP5, even if you have an extra jumper for JP4.
2. Momentarily closing JP5 will set the unit to full scale output (10V or 20mA). Do not press the buttons on the unit as this will affect the output calibration. If the receiving device does not indicate a full scale reading after JP5 is closed, verify that the wiring is correct.
3. Remove the shorting block from JP4 and restore it to its original position at jumper JP5. The TR-9200 will reset and it's output now corresponds to the actual detected CO2 concentration.

Cover Replacement

Engage the top center of the cover under the latch at the top of the base, then press the bottom of the cover onto the base until it latches.

Field Adjustments

This section describes the features that can be field configured and the procedures to make these changes.

Analog Output Range Adjustment

This section refers to advanced features of the TR-9200. 2000 ppm users need not perform this adjustment.

The TR-9200 ships from the factory set for an analog output range of 0 to 2000 ppm. This range can be changed to any sub-range between 0 and 5000 ppm by changing two parameters:

The low output threshold is the concentration at which the analog output will begin to rise. The factory default low output threshold value is 0.

The high output threshold is the concentration at which the analog output reaches its maximum value. The factory default high output threshold value is 2000.

For example, a particular application may require the analog output to remain at 0V or 4.0 mA until the gas concentration reaches 500 ppm, then reach 10V or 20 mA at a concentration of 1000 ppm. In this example the analog output would scale across this 500 ppm sub-range so that the analog output would be at half scale (5V or 12 mA) at 750 ppm.

To change the analog output range use the following procedure:

1. Note whether the shorting block at jumper JP5 is covering both pins or only a single pin, then borrow the shorting block and slide it over the two pins of jumper JP4 (see Figure 2 on page 2). The display (if present) will show 'SEL'. Be sure to remove the jumper from JP5, even if you have an extra jumper for JP4.
2. The display (if present) will show 'SEL'. Momentarily closing a jumper selects which value to change. If the wrong jumper is selected simply open JP4 to restart the unit and begin again.
3. Select the low output threshold by momentarily closing JP1.
   
   If the display is present it will show the current low display threshold. If there is no display the value can be displayed using a meter connected to the analog output. In this calibration mode the analog output is 10,000 ppm at full scale (i.e. 10.0 volts or 20.0 mA). If the voltage output is selected, this scaling corresponds to 1 ppm per millivolt or 1000 ppm per volt.
4. Use the 'UP' and 'DOWN' buttons to adjust the low output threshold to the desired value. In the example this would be set to 500.
5. Remove the shorting block from JP4 to save the value; the unit will reset itself.
6. Reconnect JP4. The display (if present) will show 'SEL'. Select the high output threshold by momentarily closing JP2. If present, the display will show the high output threshold. If there is no display use a volt meter as described in step 3.
7. Use the 'UP' and 'DOWN' buttons to adjust the high output threshold to the desired value. In the example this would be set to 1000.
8. Remove the shorting block from JP4 and restore it to its original position at jumper JP5. The TR-9200 will reset and its output will now only change when the gas concentration is within the range selected. Below this range the output remains low, above this range the output remains high.

Altitude Correction

The TR-9200 is factory-calibrated for operation at sea level. When operated at higher elevations, the calibration must be adjusted by the amount shown in the altitude correction table to the right.

Altitude Correction Procedure

To adjust the calibration of a unit currently calibrated for sea level operation to a new altitude proceed as follows:

1. Let the TR-9200 stabilize to the ambient CO2 concentration, and record the reading in ppm.
2. Multiply the reading by the scale factor corresponding to the operating altitude in the altitude correction table. For instance if the unit is operating at an altitude of 4000 ft, the scale factor from the table is 1.14. If the concentration reads 420 ppm, multiply 420 times 1.14 giving 478 ppm. Adjust the display to read 480.
3. Remove the TR-9200's cover (see removal procedure).
4. Note whether the shorting block at jumper JP5 is covering both pins or only a single pin, then borrow the shorting block and slide it over the two pins of jumper JP2 (see Figure 2 on page 2). Be sure to remove the jumper from JP5, even if you have an extra jumper for JP2. 5. Use the 'UP' and 'DOWN' buttons to change the concentration to the value just calculated.
   

   ALTITUDE CORRECTION TABLE
   Altitude [feet]	Multiplication Factor
   0	1.0
   500	1.02
   1000	1.03
   1500	1.05
   2000	1.07
   2500	1.08
   3000	1.10
   3500	1.12
   4000	1.14
   4500	1.16
   5000	1.18

    

5. Remove the shorting block from jumper JP2 and return it to its previous position over one or both pins of jumper JP5.
6. Replace the cover (see procedure).

Calibration

This section describes the calibration verification procedure and calibration adjustment procedures.

Verification Procedure

A quick but approximate calibration verification can be done by supplying the unit with outside air and letting the reading stabilize. CO2 concentrations in outside air are typically between 350 and 450 ppm.

A more accurate calibration check requires the use of calibration gas of known concentration. A calibration kit is available from the factory.

To verify the TR-9200's calibration, proceed as follows:

1. Remove the front cover of the unit (see procedure).
2. If there is no display on the unit being calibrated, connect a current or volt meter to the analog output terminals. Check the setting of the analog output selector (see Figure 2) to determine whether the unit is set for voltage or current output.
3. Note whether the shorting block at jumper JP5 is covering both pins or only a single pin, then borrow the shorting block and slide it over both pins of jumper JP2 (see Figure 2). Be sure to remove the jumper from JP5, even if you have an extra jumper for JP2.
4. Remove the dust cover from the calibration nipple, attach a flexible tube and establish a flow of between 50 and 100 cc/min (0.1 to 0.2 SCFM) of calibration gas through the sensor. Allow approximately two minutes for the reading to stabilize.
5. If the reading differs by more than ± 75 ppm from the known concentration of the calibration gas, use the 'UP' and 'DOWN' buttons (see Figure 2) to adjust the reading.
6. When the reading agrees with the concentration of the calibration gas, remove the shorting block on jumper JP2, and replace in its original position at jumper JP5.
7. Turn off the calibration gas flow, disconnect the gas tubing from the calibration nipple and replace its dust cover. Remove the meter leads from the terminal strip and replace the front cover
   (see procedure).

High CO2 Limit

An adjustable high CO2 limit is a standard feature of the TR-9200. The front panel LED changes from steady to blinking when the indicated concentration is above the high CO2 limit value. An optional contact closure is available which opens or closes when the high limit is exceeded.

Adjusting the High CO2 Limit

The setpoint value is adjusted by closing jumper JP3 (see Figure 2 on page 2). If the display is present when JP3 is closed it will show the current high limit setpoint in ppm CO2.

If there is no display this setting can be adjusted by using a meter connected to the output. In this calibration mode the analog output is 10,000 ppm at full scale (i.e. 10.0 volts or 20.0 mA). If the voltage output is selected, this scaling corresponds to 1ppm per millivolt or 1 volt per 1000 ppm.

The setpoint is adjusted with the 'UP' and 'DOWN' buttons while JP3 is closed. When JP3 is opened, the new relay setpoint takes effect and is stored in non-volatile memory. The setpoint hysteresis is approximately 40 ppm.

Optional High Limit Contact

The high CO2 limit option provides a dry (i.e. unpowered) contact closure that activates when the detected concentration rises above the high CO2 limit. The high limit is adjustable from 0 to full scale of the unit

Setting High Limit Contact Polarity

The polarity of the high limit contact is set with jumper JP5 as shown in the table below.

To open jumper JP5 remove the shorting block from the two pins, and replace it so that it engages only a single pin of the jumper. The shorting block should not be removed; it is required during the calibration procedure.

Duct Sampling Option

Figure 3

Overview

The duct sampling option is used to divert a portion of the duct airflow through the TR-9200. The difference between the total pressure at the upstream sample port and the static pressure at the downstream return port propels the sample stream. Minimum recommended flow rate is 200 feet per minute.

A TR-9200 with the duct sample option has a sample draw adapter fitted to the bottom of its enclosure. The duct probe assembly is connected to tubing nipples on the adapter.

Duct Kit Contents 

• 1 dust filter 2 sheet metal screws 
• 1 duct probe assembly 
• 2 lengths of 1/8" ID tubing

Duct Kit Installation

1. Select a point along the duct where the probe assembly can be installed into unrestricted airflow without interfering with any internal components such as dampers, radiators, etc.
2. Mark and drill the four holes for the duct probe as shown in Figure 4. The centerline must be parallel to the air flow through the duct.
3. Install the duct probe assembly through the holes just drilled. The sample port must be on the upstream side. Secure the probe assembly in place with two sheet metal screws.
4. Connect the open ends of the two tubes from the probe assembly to the two sample ports on the base of the Model TR-9200. It makes no difference which tube is connected to which port on the TR-9200.

Figure 4

Limited Warranty and Remedies

AirTest warrants to Buyer of the AirTest TR-9200 that for 18 months from the date of shipment of Products to the Buyer that Products will substantially conform with the product specifications agreed to by AirTest. This warranty is not transferable.

This warranty does not cover:

Defects due to misuse, abuse, or improper or inadequate care, service or repair of Products;

Defects due to modification of Products, or due to alteration or repair by anyone other than AirTest; or

Problems that arise from lack of compatibility between AirTest' Products and other components used with those Products or the design of the product into which Products are incorporated. Buyer is solely responsible for determining whether Products are appropriate for Buyer's purpose, and for ensuring that any product into which Products are incorporated, other components used with AirTest' Products, and the purposes for which AirTest' Products are used are appropriate and compatible with those Products.

The warranty in this section is in lieu of all other warranties, express or implied. AirTest expressly disclaims all implied warranties, including the warranties of merchantability and fitness for a particular purpose AirTest is not responsible in any way for damage to a product, property damage or physical injury resulting in whole or in part from (1) Improper or careless use, (2) Unauthorized modifications or (3) Other causes beyond the control of AirTest. In no event is AirTest liable to the buyer or any other person for cost of procurement of substitute goods, loss of profits, or for any other special, incidental or consequential damages.

Dimensions

1. TR-9200 Layouts

Wire Diagrams

1. TR-9200 Wiring