Instruction Manual

32
tina46e1-a (2010-03) BPG402.om
Bit 7 Bit 3 Bit 1 Bit 0 Definition
x x x x not used
Bit 6 Bit 5 Bit 4 Bit 2 Definition
x x x 1 Pirani error
x x 1 x hot cathode error
2)
x 1 x x hot cathode warning
3)
1 x x x electronics error / EEPROM error
2)
Both filaments broken
3)
One filament broken
The software version of the gauge can be calculated from the value of byte 6 of the
transmitted string according to the following rule:
Version No = Value
Byte 6
/ 20
(Example: According to the above formula, Value
Byte 6
of 32 means software ver-
sion 1.6)
The pressure can be calculated from bytes 4 and 5 of the transmitted string. De-
pending on the currently selected pressure unit (→ byte 2, bits 4 and 5), the ap-
propriate rule must be applied.
As result, the pressure value results in the usual decimal format.
p
mbar
= 10
((high byte × 256 + low byte) / 4000 - 12.5)
p
Torr
= 10
((high byte × 256 + low byte) / 4000 - 12.625)
p
Pa
= 10
((high byte × 256 + low byte) / 4000 - 10.5)
The example is based on the following output string:
Byte No 0 1 2 3 4 5 6 7 8
Value 7 5 0 0 242 48 20 12 71
The instrument or controller (receiver) interprets this string as follows:
Byte No Function Value Comment
0 Length of
data string 7 set value
1 Page number 5 hot cathode gauge
2 Status 0
emission = off
pressure unit = mbar
filament 1 active
3 Error 0
no error
4
5
Measurement
High byte
Low byte
242
48
calculation of the pressure:
p = 10
((242 × 256 + 48) / 4000 - 12.5)
= 1000 mbar
6 Software version 20
software version = 20 / 20 = 1.0
7 Sensor type 12 BPG402-Sx
8 Check sum 71
5 + 0 + 0 + 242 + 48 + 20 + 12 =
327
dec
01 47
hex
High order byte is ignored ⇒
Check sum = 47
hex
71
dec
Error byte
Software version
Calculation of the pressure
value
Example