11
Operation
6 Operation
6.1 Before switching on
After switching on the power supply, the transmitter is ready for operation. However, it is
advisable to wait for a stabilization period of 5-10 minutes before measurement, and to
operate the transmitter without interruption during the measurement process.
The pressure measured in the Pirani range depends on the gas type. To adjust for differ-
ent gases, a corresponding gas type correction factor can be set on the transmitter; this
generates correct measurements in the pressure range below 1 mbar. The gas type cor-
rection factor is factory-set for air and N
2
to 1.00 (see p. 18, chap. 10.3).
6.2 Configuring the data exchange
Communication is carried out, depending on the address selector switch setting, via the
serial RS-232 interface using the relevant display units or via RS-485 using the Pfeiffer
Vacuum protocol:
● 9600 baud
● 8 data bits
● 1 stop bit
● no parity
Parameter overview
Parameters are displayed in square brackets as a three-digit number in bold font. The
designation may also be stated if necessary.
Example: [P:312] Software version
Reading the actual
pressure value
[P:740]
Pressure value as the value to be queried and also as equalization (see below) are trans-
mitted by means of a string in the format "aaaabb", whereby "aaaa" is the mantissa and
"bb" the exponent with offset 20 of an exponential number. "aaaa" is therefore in the
range "1000" (for 1.000) to "9999" (for 9.999). The individual characters of the string are
the numbers "0" (ASCII 48) to "9" (ASCII 57).
Example: "104223" represents 1.042 x 10
+3
mbar, "750015" represents 7.500 x 10
-5
mbar.
# Name Data type Handling
CPT 100
PPT 100
RPT 100
HPT 100
MPT 100
40 DeGas 6 - boolean_new readable, writable
•
41 Sensor on/off 7 - u_short_int readable, writable
•
•
49 Switch mode 7 - u_short_int readable, writable
•
•
•
303 Actual error code 4 - string read-only
•
•
•
•
•
312 Software version 4 - string read-only
•
•
•
•
•
349 Component name 4 - string read-only
•
•
•
•
•
740 Pressure in [mbar] 10 - u_expo_new readable, condition-
ally writable
•
•
•
•
•
741 Pressure set point 7 - u_short_int only writable
•
•
•
•
•
742 Correction value
(Pirani)
2 - u_real readable, writable
•
•
•
•
743 Correction value
(Bayard-Alpert)
2 - u_real readable, writable
•
743 Correction value
(CC sensor)
2 - u_real readable, writable
•
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