INFICON BPG400 ATM to Ultra-High Vacuum Gauge User Manual
Page 33
tina03e1-b (2004-02) BPG400 v1.om
33
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
10
69
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
BPG400
2
Status
0
Emission = off
Pressure unit = mbar
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
10
BPG400
8
Check sum
69
5 + 0 + 0 + 242 + 48 + 20 + 10 =
325
dec
01 45
hex
High order byte is ignored
⇒
Check sum = 45
hex
69
dec
For transmission of the commands to the gauge, a string (frame) of five bytes is
sent (without <CR>). Byte 1 to byte 3 form the data string.
Byte no Function
Value
Comment
0
Length of data string
3
(Set value)
1
Data
→ admissible input strings
2
Data
→ admissible input strings
3
Data
→ admissible input strings
4
Check sum
(from bytes No 1 … 3)
0 … 255
(low byte of sum)
1)
1)
High order bytes are ignored in the check sum.
For commands to the gauge, six defined strings are used:
Byte No
Command
0
1
2
3
4
2)
Set the unit mbar in the display
3
16
62
0
78
Set the unit Torr in the display
3
16
62
1
79
Set the unit Pa in the display
3
16
62
2
80
Power-failure-safe storage of current unit
3
32
62
62
156
Switch degas on
(switches itself off after 3 minutes)
3
16
93
148
1
Switch degas off before 3 minutes
3
16
93
105
214
2)
Only low order byte of sum (high order byte is ignored).
Example
4.6.1.2 Input String (Receive)
Format of the input string
Admissible input strings