INFICON HPG400 ATM to High-Vacuum Gauge User 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
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