2-point RH adjustment of HMP70 series probes - HM70

HM70 User Guide

Document code
M210297EN
Revision
G
Language
English (United States)
Product
HM70
Document type
User guide

Low humidity references 0 % (Nitrogen) / 11.3 % (LiCl) and higher humidity references 75 % (NaCl) / 97 % (K2SO4) are recommended for 2-point adjustment.

  • The difference between the low and high reference must be at least 30 %RH
  • The low reference can be at most 15 %RH
To make a 2-point adjustment:
  1. When adjusting both relative humidity and temperature, make the temperature adjustment first.
  2. Check that HM70 is turned on.
  3. If the chemical purge option is available, perform it before adjustment. For instructions, see Chemical purge (optional).
  4. Detach the screw from the probe handle to expose the calibration button.
  5. Press the calibration button in the probe handle with a thin sharp-pointed tool, such as a small screwdriver. Pressing the button switches the indicator to adjustment mode.
  6. Press OK to start the adjustment mode.
  7. Choose RH and press Select.
  8. Press Yes to check the environment settings. To continue adjustment directly without checking the environment settings, press No.
  9. The adjustment mode is now on. Press Adjust to select the adjustment method.
  10. Choose 2-point adjustment and press Select.
    To carry out the LiCl-NaCl automatic adjustment described in LiCl-NaCl automatic RH adjustment of HMP70 series probes, choose LiCl--NaCl autom. instead.
  11. Set the probe to the lower reference relative humidity. If using Vaisala Humidity Calibrator HMK15, use the adapter fitting (13.5 mm hole) with HMP76 and HMP77 probes. You can follow the stabilization from the graphical display by pressing Graph. Press Ready when the reading has stabilized.
  12. Enter the correct lower reference humidity value with the arrow buttons and press OK.
  13. Set the probe to the higher reference relative humidity. You can follow the stabilization from the graphical display by pressing Graph. Press Ready when the reading has stabilized.
  14. Enter the correct higher reference humidity value with the arrow buttons and press OK.
  15. Confirm the adjustment by pressing Yes. If you press No, you return to the adjustment mode display and no changes are made.
    If the difference between the 2 references is less than 30 %, the adjustment cannot be done.
  16. The adjustment is done. Press Back and Exit to return to the basic display.
  17. Replace the screw on the calibration button.

    You can attach a sticker on the calibration button screw to seal the calibration.