
Manufacturer Specific Profile Area
CAN-CBX_Pt100
Manual • Doc.-No.: C.3032.21 / Rev. 1.1
Page 99 of 120
8.11.2 ADC_PGA (2400
h
)
Index
Sub-
index
Description
Value range
Default
Data type
Access
mode
2400
h
0
Number_of_entries
4
4
unsigned 8
ro
1
ADC_PGA_1
1...4
3
unsigned 8
rw
2
ADC_PGA_2
1...4
3
unsigned 8
rw
3
ADC_PGA_3
1...4
3
unsigned 8
rw
4
ADC_PGA_4
1...4
3
unsigned 8
rw
Description of the parameter ADC_PGA_x (x = 1...4):
This parameter sets the gain (PGA) of the A/D-converters (ADS1255).
Value range:
The gain V
x
is:
V
x
= 2
ADC_PGA_x
The gain 2, 4, 8 and 16 can be adjusted. The gain is transparent for the user and already included in
the calculation of the firmware.
Attention:
For the connection of measuring resistors the following voltage limits have to be
considered: Voltage limitation by input circuit: U
maxph
= 1.25 V
Depending on ADC_PGA_x the maximum permissible resistor values are:
Gain
(ADC_PGA_x)
Input voltage
U
FS
[V]
max. permissible
electrical resistance
at a measuring current of
ca. 400
E
A
ca. 40
E
A
1
± 2.5
3 k
F
34 k
F
2
± 1.25
3 k
F
34 k
F
3
± 0.6125
1.5 k
F
17 k
F
4
± 0.306
773
F
8.5 k
F
Note:
The recommended gain is ADC_PGA_x =3.