Installation and Operation Guide | DGS Modbus
© Danfoss | ADAP-KOOL® | 2016.12
16 | RS8HJ102 |
Step
Bump Testing Using Gas Ampoules
1
Make sure that both the ampoules and the calibration
beaker are clean and dry.
2
Unscrew the beaker hold screw and place the ampoule
so that it sits in the base of the beaker (see Figure 7).
3
Tighten wing-nut screw onto the ampoule without
breaking it.
4
Remove the enclosure lid of the gas detector.
5
Connect a voltmeter to monitor sensor response. Moni-
tor response (0-5V) between pins 0V (TP3) and Vs (TP2).
6
Place the beaker over the sensor head using the multi
sensor adaptor to fit the sensor, or, if an Exd, IP66 or
Remote sensor head version, screw the beaker on the
remote sensor head M42 thread or M35 thread adaptor.
It should be as tight fitting as possible to allow maxi-
mum gas exposure.
7
Tighten the wing-nut screw onto the ampoule until it
shatters allowing the gas to diffuse in the beaker. It
should be left in place for approximately 5 min.
8
The voltage output will increase. This confirms that the
sensor is responding. A response equivalent to at least
50% of the test gas (typical) will confirm that the system
is in order.
9
Remove the beaker from the sensor. Carefully remove
any ampoule remains from the gas detector and beaker.
6.3 Calibration Overview
There are two adjustments required: zero and span. They are
monitored at testpoint TP2 and TP3 using a 0-5V scale. See fig. 1.
If the sensor range is 0-1000 ppm, then 5V=1000 ppm.
Tools required:
• Gas cylinder with the appropriate gas and concentration
• Calibration kit
• A voltmeter (crocodile clips recommended)
• Screwdriver (depending on housing).
Danfoss offers calibration gasses and a kit that consists of a flow
regulation valve with flexible non-absorbent tubing and vented
calibration hood. (see fig. 6).
NOTE
: For improved accuracy and response, the instrument
should be zeroed and calibrated in the environment in which it is
being installed.
6.4 Calculating Calibration Voltage
Sensor outputs are linear. As long as you have a gas cylinder of
known concentration you can calibrate to any desired range*.
However, for maximum accuracy calibrate with a gas close to the
alarm set point.
Example: For a sensor range of 0-1000 ppm and a cylinder of the
target gas at 800 ppm:
Voltage = Target Gas Value ×_____5 V_____
Sensor Range
Voltage = 800 ppm × ___5 V____ _
1000 ppm
= 4 V
So the output voltage signal should be adjusted to 4V.
*For R449A only: This gas is nonlinear above 500ppm. Calibration must be done with
a 500 ppm gas. Any readings above 500ppm must be regarded as in-valid. 500ppm is
also the maximum allowed alarm threshold for this gas.
6.5 Calibrating Semiconductor (SC) Sensors
Step
Calibrating Semiconductor (SC) Sensors
1
Locate P2 which is used to adjust the zero point.
2
Monitor the output between 0V (TP3) and Vs (TP2).
3
Expose sensor to zero air until output is stable (typically
3-5 minutes).
4
Adjust P2 until the voltmeter reads a slightly positive
value (0.01 V is acceptable).
5
Locate P3 which is used to calibrate the range (span) of
the sensor.
6
Expose the sensor to calibration gas and allow to stabi-
lise (typically 3-5 minutes).
7
Adjust P3 until the voltmeter equals the voltage calcu-
lated in section 6.4
NOTE:
For semiconductor sensors, you MUST use calibration gas
in a balance of air (
not
N2).
6.6 Calibrating Infrared (IR) Sensors
Step
Calibrating Infrared (IR) Sensors
1
Locate P2 which is used to adjust the zero point.
2
Monitor the output between 0V (TP3) and Vs (TP2).
3
Expose the sensor to nitrogen or zero air until output is
stable (typically 3-5 minutes).
4
Adjust P2 until the voltmeter reads 0 V or slightly posi-
tive (0.01 V is acceptable).
5
Locate P3 which is used to calibrate the range (span) of
the sensor.
6
Using the appropriate calibration hood for the sensor,
expose the sensor to calibration gas and allow to stabi-
lise (typically 3-5 minutes).
7
Adjust P3 until the voltmeter equals the voltage calcu-
lated in section 6.4
6.7 Calibration of alarm setpoint
See section 4.3
6.9 Issue Test certificate
See example in appendix C
6.8 Calibration of 4-20mA output
For improved accuracy of the 4-20mA output it is possible to zero
adjust this separately. This is done by adjusting the potentiometer
P4 until the output corresponds to the gas concentration:
Current = 4mA + gas concentration ×_____16 mA____
Sensor Range
Example for a sensor range of 0-1000ppm and a gas concentration
of 800ppm:
Current = 4mA + 800 ppm × ___16mA____ _
1000 ppm
= 16.8mA
