Making a 1-point adjustment - GM70

GM70 User Guide

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User guide
CAUTION Make sure to check the following when carrying out the adjustment:
  • Give the correct reference concentrations in the correct units
  • Wait until the reading has fully stabilized before accepting the reading.

Reverting to factory settings is not possible after the adjustment.

See also Field Check Adapter 26150GM Quick Reference Guide (M210450EN), available at
  1. Insert the probe into the field check adapter (as deep as possible, the perforated filter cover should be completely inside the adapter).
  2. Connect the tubing to the bottom port of the adapter.
  3. Connect the adapter with the tubing to the flow meter, the pressure regulator and further to the reference gas bottle. The side port of the adapter is left open for gas outflow.
  4. Let the low end reference gas flow and stabilize with a flow rate of about 0.6 l/min. Follow the reading of GM70 and wait until the reading has fully stabilized. .
  5. Take out the screw from the GM70 probe handle to expose the adjustment button (see Figure 1). Press the button with a small screwdriver. When pressing the button, the indicator turns to adjusting mode.
  6. Press OK to confirm that you are making an adjustment.
  7. Select CO2 and press Select.
  8. Press Yes to give the ambient pressure and temperature values. To continue adjusting, press Exit.
  9. The adjustment mode is now active. Press Graph to confirm that the readings have stabilized. Go back and press Adjust to select the adjustment method.
  10. Select 1-point adjustment and press Select. Press Ready when the value has stabilized.
  11. Give the reference concentration value by using the arrow buttons and press OK.
    For example, if you are using pure nitrogen, enter value 0 ppm. For other reference gases, the analyzed CO2 concentration is typically printed on the bottle: use that value. Take care that you give the correct value in correct units, as you cannot revert the earlier values after accepting the new values.
  12. Confirm the adjustment by pressing Yes. If you press No, you return to the adjustment mode display and changes are canceled.
  13. The adjustment is complete. Press Back and Exit to return to the basic display.
  14. Shut off the gas flow.
  15. Replace the screw onto the adjusting button.