INFICON HPG400 ATM to High-Vacuum Gauge - Manual (Page 30)

30
tina31e1 (2004-05) HPG400 v1.om
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 11 63
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 (Set value)
2 Status 0 Emission = off
Pressure unit = mbar
3 Error 0 No error
4
5
Measurement
High byte
Low byte 235
48
Calculation of the pressure:
p = 10
(235 × 256 + 48) / 1333.3 - 42.5
= 454 mbar
6 Software version 20 Software version = 20 / 20 = 1.0
7 Sensor type 11 (HPG400 gauges)
8 Check sum 63 5 + 0 + 0 + 235 + 48 + 20 + 11 =
319
dec
01 3F
hex
High order byte is ignored
⇒
Check sum = 3F
hex
63
dec
For transmission of the commands to the gauge, a string (frame) of five bytes is
sent (without <CR>). Byte No. 1 … 3 form the data string.
Byte No. Function Value
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, the following 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
2) Only low order byte of sum (high order byte is ignored).
Example
4.5.1.2 Input String (Receive)
Format of the input string
Admissible input strings