LEYBOLD THERMOVAC TTR 101 N, Руководство по эксплуатации

Страница: 23 / 42

23 300544655_002_C1 - 11/2016 - © Leybold
5.3
Sensor gas dependence
The sensor technology is based on measurement of thermal conductivity (for the MEMS Pirani-sensor) and
consequently its reading depends on gas and gas concentration. The default analog output will provide a combined
reading of the gas dependent MEMS Pirani sensor reading and the gas independent Piezo sensor reading as
described in chapter 5.1. Thus only a part of the combined measurement range, from 5x10
-5 to 14.7 mbar, will be
gas dependent. The transmitter has calibration curves for a number of common gases. For gas setup, please refer
to the Communication Protocol 300544663 (RS232) and 300544664 (EtherCAT). The transmitter sensor is per
factory default calibrated for Nitrogen gas and shown below is the TTR 101 N THERMOVAC MEMS Pirani reading
for different gas types. Be aware that when measuring in environments where other gases than nitrogen
(calibration gas) are present, the readings can deviate from the true pressure.
In the range below 1 mbar, the pressure indication is linear. For gases other than air, the pressure can be
determined by means of a simple conversion formula:
𝑝
𝑒𝑓𝑓
= 𝐶 . 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑟𝑒𝑎𝑑𝑖𝑛𝑔
For which:
Gas type Calibration factor C Valid range (mbar]
He 1.4 3∙10
-3
to 0.3 mbar
Ar 1.57 10
-3
to 1 mbar
H
2
0.84 3∙10
-3
to 0.2 mbar
Air, O
2
, CO, N
2
1
3∙10
-3
to 0.3 mbar
These conversion factors are average values.
1E-4
1E-3
1E-2
1E-1
1E0
1E1
1E2
1E3
1E-4 1E-3 1E-2 1E-1 1E0 1E1 1E2 1E3
A
ct
u
al
g
as
p
re
ssu
re
, m
b
ar
Transmitter reading, mbar
Air (MEMS Pirani)
Argon (MEMS Pirani)
Helium (MEMS Pirani)