RKI Instruments HS-94 - Manual (Page 10)

2. While continuing to hold the AIR Button, press also the MODE button until
instrument beeps.
3. After the beep, release the MODE button but continue to hold the AIR button
for a few seconds until the display completes warmup and reads the gas
concentration. Just to the left of the gas reading there will be a small arrow
pointing downward. This indicates that the instrument is ready to set the zero
reading.
Zeroing the instrument:
4. Apply the zero gas. For the H2S or CO units, the Zero gas can be the
surrounding ambient air if it is known to be gas free. For the Oxygen version,
expose the sensor to a known oxygen free sample such as 100% nitrogen. Flow
the gas onto the sensor using a test cup covering the sensor area on the top of
the unit, and allow sufficient time for the reading to stabilize, typically 30 to 60
seconds. If you wish to skip the zero adjustment, press the MODE switch and
continue to step 7.
5. Once full reading is reached, press the AIR button for about 5 seconds. The unit
will beep 3 times initially, and then two more times to indicate that it has
completed the adjustment.
Calibrating the instrument:
6. Press the MODE switch one time. The small arrow on the display to the left of
the gas reading will change to pointing upward, indicating that the instrument is
now in the “span set” mode.
7. For H2S or CO units, go to step 8. For Oxygen units, take the instrument to fresh
air, press and hold the AIR button until the unit has beeped 5 times. The last 2
quick beeps indicate that the unit has completed the calibration adjustment. Now
press the mode switch once to return to normal operation.
8. For H2S and CO units, after step 6 above, the display will read a value that the
instrument believes is the concentration of the calibration gas that will be
applied. If the value displayed matches the value of the calibration gas that you
will apply, then go to step 9. If it does not match, then press the AIR button to
scroll the reading to the correct value of your calibration gas. Note that the
readout will only scroll up, but will return to Zero and start over after it reaches
1 0