Set Pressure Value for Dew Point Calculation

Set Pressure Value for Dew Point Calculation - DMT132

DMT132 User Guide

Document code

M211289EN

Revision

Language

English

Product

DMT132

Document type

User guide

The HUMICAP® 180R sensor in the DMT132 is not very pressure-dependent. However, to maximize the measurement accuracy, the pressure of the system must be known. The pressure compensation value has been set at the factory according to the order form. You can view and set a new value using the PRES command.

It is important to set the pressure compensation value accurately when the transmitter is configured to output dew point temperature in atmospheric pressure (T_d/f atm). For standard dew point measurement (T_d/f), it is enough to set an approximate pressure value (±1 bar).

PRES [pp.ppppp]<cr>

pp.ppppp: Absolute pressure (bar_a ) in the measuring point. Range 0 ... 20 bar.

Example:

>pres 1.01325
>Pressure (bar)      : 1.01325
Saving settings...done
>

The pressure conversion coefficients from other pressure units to bars is given in the table below.

Table 1. Pressure Conversion Coefficients
From	To bar_a
PaN/m²	0.00001
mmHg torr	0.001333224
inHg	0.03386388
mmH₂O	0.00009806650
inH₂O	0.002490889
atm	1.01325
at	0.980665
psi_a	0.06894757

For example:

$29.9213 i n H g = 29.9213 \times 0.03386388 = 1.01325 {b a r}_{a}$

Conversions from mmHg and inHg are defined at 0 °C and from mmH₂O and inH₂O at 4 °C.

You can also set the pressure compensation value when you connect the DMT132 to the MI70 indicator. When using the MI70, the pressure unit is bar_a.