RKI Instruments NP-204 - Manual (Page 11)

NP-204 RKI Instruments, Inc.
Caution
The combustibles measurement (low range) is flow-sensitive. Use a flowmeter and set the flow rate
to 0.8 SCFH (0.4 l/m).
7 . Remove the span gas tubing from the probe, and place the probe in fresh air.
Squeeze the bulb 5 times to expose the sensor to fresh air, and then verify that
the combustibles reading returns to zero.
8 . Repeat the exposure to the calibrating sample and verify that the combustibles
reading reaches the correct level. Readjust and repeat from step 3 until no
further adjustment is required.
9 . If the combustibles reading cannot be set high enough to agree with the
calibrating sample, replace the sensor.
Maintenance
Batteries
1 . Check the battery voltage periodically by turning the Range switch to the VOLT
ADJ. position, and verifying that the voltage can be set to the red Volt check line.
Replace the batteries if the voltage cannot be set to the Volt check line.
WARNING
Take the NP-204 to a non-hazardous location before replacing the batteries.
2 . The batteries are located in a compartment on the bottom of the case. To replace
the batteries, loosen the screw on the bottom of the case, and remove the battery
compartment cover. Remove the batteries and verify that the battery
compartment and electrical contacts are clean. If necessary, use a soft wire
brush to gently clean the compartment and contacts. Insert fresh batteries
(alkaline or fully-charged Ni-Cd) according to the polarity (+/-) markings on
the battery holder diagram, and replace the cover.
Sensor Maintenance
Combustibles sensor (Low range sensor) life is generally related to usage, but certain environmental
factors may affect duration. Exposure to high concentrations (above 5% volume) will reduce the life of
the low range sensor. The Thermal conductivity sensor (High range sensor, or TC sensor), is an
extremely stable sensor that generally will last for several years. However, if liquid is drawn into the
instrument, both sensors could be ruined.
If a sensor requires replacement, call RKI or your local distributor.
Low Range Sensor
Replace the low range sensor filaments when:
1 . The low range cannot be calibrated correctly.
2 . The low range cannot be set to zero after warmup using the external ZERO ADJ.
knob.
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