9
A100b
JAN 2009
LED LOGIC
GAS SENSOR LED INDICATORS
LED OPER ATIONS
RESULT
Green LED Flashing / Red LED off
Warming up ≈ 5 min
Green LED on / Red LED off
Ready to detect gas
Green LED on / Red LED on
Gas level above gas
sensor trip point
Green LED off / Red LED on
Sensor element
failure or sensor
disconnected
Green LED off / Red LED flashing
Low supply voltage or
low supply current
CALIBRATION PROCEDURES
Refer to Fig. E for calibration of Hansen sensors.
Equipment required:
Hansen calibration kit, stopwatch, hex wrench; 5/32 ˝,
long nose pliers, 24V AC/DC power supply, voltmeter,
2 minigrabber voltmeter leads and calibration gas for
the specific sensor.
Setup:
Be sure the system is made safe during
1.
calibration. The 4-20mA output and internal relay
will be active during calibration.
Be sure the gas sensor has been powered up
2.
for a minimum 24 hours to stabilize the sensing
element.
Verify the green LED is illuminated and the red
3.
LED is off.
Disable the internal horn by removing JP2 jumper.
4.
Zero Calibration:
Set the voltmeter to the appropriate DC range. The
5.
sensor element output is measured in DC volts;
zero volts equals zero PPM and 5 volts equals the
gas sensor PPM rating. (i.e. 100PPM, 250PPM).
Attach the voltmeter leads to the VS, (+) lead from
the voltmeter, V0, (-) lead of the voltmeter.
Be sure the ambient atmosphere around the gas
6.
sensor is free of the target gas.
Adjust the zero potentiometer (Z) until the voltage
7.
reading on the voltmeter reads between zero
volts and +/- 0.090VDC.
Span Calibration:
Always per form the zero calibration before doing
1.
the span calibration.
Place the boot over the sensor element. Use
2.
the correct concentration of calibration gas for
the full range of the sensor. In other word, for a
gas sensor with a range of 0 to 250 PPM, use a
250 PPM calibration gas when setting the span.
If full range calibration gas is not available, a
calibration gas of less than full range can be used
then adjust to the corresponding output voltage.
This may result in some loss of accuracy.
3a.
Gas sensors (except Vent line).
Star t the flow of gas. Obser ve the output, it
should begin to increase after 5 seconds. Leave
the gas flow on and obser ve the voltage. The
sensor voltage will slowly climb toward 5VDC.
When the voltage does not change by more than
+/- 0.010 volts per 15 seconds the sensor output
voltage is considered to be stable. Adjust the
span potentiometer (S) so the output voltage
reads between 4.95 to 5.00 volts DC.
3b.
Vent line gas sensors.
Star t the flow of gas. Obser ve the output, it
should begin to increase after 5 seconds. Leave
the gas flow on and obser ve the voltage. The
sensor voltage will ramp up ver y quickly crest
then decrease quickly. At this point, adjust the
span potentiometer (S) so the output reads
between 4.95 to 5.00 volts DC.
4. Stop the flow of gas and remove the boot from the
sensor element. Verify the sensor voltage output
begins to decrease.
5. Do not attempt to re-adjust the zero or span
calibration until another 24 hours of powered
operation has passed.
6. Enable system. Verify proper operation.
7. Enable the internal horn by installing JP2 jumper.
Electrochemical Sensor Only (Zero Offset)
If the gas sensor is calibrated in the environment for
which it will be used a final zero adjustment will not be
necessar y. If the gas sensor will be calibrated at one
temperature (70ºF, 21ºC) then moved to its operating
environment (-4ºF, -20ºC) a maximum zero offset of 2%
will occur. If unacceptable, adjust the zero point as
described in section
Calibration Procedures, Zero
Calibration
. At (-40ºF, -40ºC), a maximum zero offset
of 12% will occur. If unacceptable, adjust the zero point
as described in section
Calibration Procedures, Zero
Calibration
.
CALIBRATION GAS CYLINDERS
Warning: Refer to Material Safety Sheet supplied with
gas cylinder and local safety precautions for proper
usage, handling and disposal.
Hansen calibration gas standards are traceable to NIST
(National Institute of Standards and Technology) and
analysis data is available on request.
A variety of calibration refrigerant gases and PPM ranges
are available, refer to Page 19. For special mixtures,
consult factor y. Calibration gas should be stored in a
cool area, 65ºF/75ºF. Shelf life labeled on cylinder−one
year from date of manufacture.
Calibration gas must be shipped according to Department
of Transportation Hazardous Gas Regulations. Special
shipping charges will apply. Shipping only available in
the continental USA. For shipments outside the USA,
consult Hansen for local distributors.
