Set pressure value for ppm calculation - DMT152

DMT152 User Guide

Document code
M210865EN
Revision
K
Language
English
Product
DMT152
Document type
User guide

The DRYCAP 180U sensor in DMT152 is not pressure-dependent. When measuring dew point, pressure compensation is not needed. However, in the calculation of ppm volume concentration, the pressure of the system must be known. If you did not specify pressure compensation when ordering the product, use the commands below to enable the pressure compensation and set the pressure value.

Table 1. PRES and XPRES command
Syntax Description
PRES [pp.pppp]<cr>

[pp.pppp] = Absolute pressure in the measuring point. The unit is bara if metric units have been selected, and psia if non-metric units are used.

XPRES [pp.pppp]<cr> [pp.pppp] = Absolute pressure in the measuring point. The unit is bara if metric units have been selected, and psia if non-metric units are used.

Use the XPRES command if the value is changed frequently. The value set using the XPRES command overrides the PRES value, but it is not retained at reset. When the XPRES value is set to 0, the last value set with PRES is used instead.

The minimum valid pressure value for both the PRES and XPRES commands is 0.1 bara.

Example:

pres 1.01325
Pressure       : 1.01325 bar

The pressure conversion coefficients from other pressure units to bars are given in Table 2.

Table 2. Pressure conversion coefficients
From To bara
PaN/m² 0.00001
mmHg torr 0.001333224
inHg 0.03386388
mmH2O 0.00009806650
inH2O 0.002490889
atm 1.01325
at 0.980665
psia 0.06894757

Example:

29.9213 inHg = 29.9213 × 0.03386388 = 1.01325 bara

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 DMT152 to the MI70 indicator. When using MI70, the pressure unit is bara.