Johnson Controls CDS-2000 User manual

Electronic Control Manual 216
Sensors and Stats Section S
Technical Bulletin CDS-2000
Issue Date 0393
© 1993 Johnson Controls, Inc. 1
Part No. 24-7691-41
Rev. —
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 12
CDS-2000 CO
2
Sensor Verification, Calibration,
and Troubleshooting Bulletin

2 S Sensors and Stats—CDS-2000 CO2Sensor Verification, Calibration, and Troubleshooting Bulletin

SSensors and Stats—CDS-2000 CO2Sensor 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.
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-2000-3 Calibration Kit, and perform the
single-point calibration procedure.
Pre-Verification
Information

4 S Sensors and Stats—CDS-2000 CO2Sensor Verification, Calibration, and Troubleshooting Bulletin
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.
Modes

SSensors and Stats—CDS-2000 CO2Sensor 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-2000-1), 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.
verify.drw
SW-2
Mounting Clips
Tubing Adapter
1/4 in. ID
Tubing
Green LED
Wiring Access
Silicone Blanket
Zero
Adjustment SW-1
Regulator
Alarm Threshold
Adjustment
with Gage
Figure 1: Verifying Operation of the CDS-2000
•a digital voltmeter with 10 mVDC resolution over a range of at least
0 to 10 VDC
•the CDS-2000-3 Calibration Kit which includes:
— a source of air with a known concentration of CO2between
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
Equipment Needed

6 S Sensors and Stats—CDS-2000 CO2Sensor Verification, Calibration, and Troubleshooting Bulletin
1. Disconnect the source of power to the CDS-2000.
2. 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 CO2concentration of the
bottled gas, (from its label) and determine the corresponding voltage
level by dividing the ppm value by 200.
Example: A 1000 ppm CO2concentration 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-2000-1 sensor. Remove the silicone blanket and metal clips if
using the CDS-2000-2.
Procedure

SSensors and Stats—CDS-2000 CO2Sensor 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.
•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-2000-3 Calibration Kit, which includes:
— a source of air with a known concentration of CO2between
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.
Single-Point
Calibration
Equipment Needed
Procedure

8 S Sensors and Stats—CDS-2000 CO2Sensor Verification, Calibration, and Troubleshooting Bulletin
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 CO2concentration of the bottled gas, and determine the
corresponding voltage by dividing the ppm value by 200. (For
example, a 1000 ppm CO2concentration 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 4.
9. Disconnect the DVM. Reconnect the flow pickup device if using the
CDS-2000-1. Remove the silicone blanket and metal clips if using the
CDS-2000-2.

SSensors and Stats—CDS-2000 CO2Sensor Verification, Calibration, and Troubleshooting Bulletin 9
•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 CO2has 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 CO2and a bottle
at 0 ppm CO2concentration 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 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 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).
Full Calibration
Equipment Needed
Procedure

10 S Sensors and Stats—CDS-2000 CO2Sensor Verification, Calibration, and Troubleshooting Bulletin
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 CO2gas 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-2000-1. Remove
the silicone blanket and metal clips if using the CDS-2000-2.