Chapter 7 – Maintenance
TestEquity 1016H-2 Temperature/Humidity Chamber
Page 7-9
How to Verify the Humidity Calibration
TestEquity recommends verifying the humidity calibration before attempting to actually perform
an adjustment. If you try to adjust the instrumentation before determining that calibration is
necessary, you may make it worse if done incorrectly.
A Vaisala HMM100 capacitive-type sensor is used to measure humidity. The HMM100 output is
configured for 0-100%RH = 0-20 mA. The HMM100 sensor specifications are:
Sensor accuracy at
–20°C to +40°C*
Sensor accuracy at
–40°C to –20°C, +40°C to +175°C*
±2%RH (0 to 90 %RH
±3%RH (90 to 100%RH)
±2.5%RH (0 to 90 %RH
±3.5%RH (90 to 100%RH)
*Note: Chamber controlled humidity range is +10°C to +85°C
The easiest way to verify the instrumentation accuracy is with an independent calibrated
humidity sensor and display. Place the sensor near the chamber’s humidity sensor, which is
located towards the right side of the conditioner fan grille. If the readings on the F4T/F4
Controller agree within the specified limits above, then no calibration adjustments are necessary.
TestEquity recommends the Vaisala HM70 Handheld Humidity/Temperature Meter with the
HMP77B Probe for verifying the humidity sensor calibration at all humidity conditions that the
chamber is capable of achieving.
For the F4T Controller:
If calibration of the controller is necessary, refer to the “F4T Touch
Screen Controller User’s Guide”.
For the F4 Controller:
If calibration of the controller is necessary, refer to the “F4
Temperature/Humidity Controller User’s Manual”.
Humidity Sensor Calibration and Maintenance
TestEquity recommends the Vaisala HM70 Handheld Humidity/Temperature Meter with the
HMP77B Probe for calibrating the humidity sensor at all humidity conditions that the chamber is
capable of achieving. Alternatively, the humidity sensor can be calibration with Vaisala HMK15
Humidity Calibrator which uses saturated salt solutions. These items are available from Vaisala
Inc. (www.vaisala.com).
The Vaisala HMM100 sensor is calibrated per the procedure in the Vaisala HMM100 User’s
Guide, which can be downloaded from
www.testequity.com/manuals
.
The humidity sensor element (Vaisala HUMIKAP 180R) is replaceable. The end of the sensor
probe has a stainless steel sintered filter (Vaisala HM47280SP), which can be removed by
unscrewing it. Handle the sensor by its outer plastic support. DO NOT TOUCH THE SENSOR
PLATE. The sensor and sintered filter can be cleaned with distilled water. Do not use any
mechanical methods. If you are unable to calibrate the sensor, first try cleaning the sensor
element and filter. If this does not help, then replace the sensor.