Vaisala HUMICAP HMP41 User's Guide download pdf (Page 69)

Chapter 5 ______________________________________________________________ Maintenance

VAISALA _______________________________________________________________________ 67

Adjustment with HMI41

You can check and adjust the HMT130 relative humidity measurement

with the HMI41 indicator and HMP41/45/46 probes. A HMI41-

connection cable is needed. Vaisala order code: 25917ZZ.

There are three adjustment modes available: offset (dry point), gain (wet

point), and two-point adjustment. All of these can be performed using the

HMI41 either as a reference meter (for example when the transmitter is

mounted in an air-conditioning channel) or only as a terminal for

visualizing and setting the transmitter's RH reading.

Offset and gain adjustments are performed the same way and differ only

in internal calculations. Select offset adjustment when the reference

humidity is < 65 %RH and gain adjustment when the reference humidity

is ≥ 65 %RH. Two-point adjustment is more accurate, and includes both

offset and gain corrections. For performing two-point adjustment, you

need two separate measurement points with a difference of at least 50

%RH between them.

Follow the general directions of connecting the HMI41 to the HMT130

and selecting the HMI41 calibrator function and then continue according

to the chosen adjustment method.

0505-187

Figure 20 Location of the HMI41 Calibration Connector

The following numbers refer to Figure 20 above:

1 = HMI41 indicator

2 = EXT connector

3 = 25917ZZ connection cable

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 95 96

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Vaisala HUMICAP HMP41 User's Guide Page 69