Rockwell Automation Liqui-Flo DBT Reach Drive - Manual (Page 25)

Installation/Wiring 2-19
Example:
Using a 100 Ohm Pt RTD (a=0.00385) to measure temperatures from 0 degrees
Celsius to 200 degrees Celsius, the maximum resistance occurs at 200 degrees
Celsius and is approximately 177 Ohm. The maximum voltage across the sensor is
151 mV. If the x40 gain is used, the output voltage at 200 degrees Celsius is 6.04
Volts.
Digital I/O
The digital outputs are isolated with solid state relays. The outputs are internally short
circuit protected. The digital input is optically isolated.
2.5.7.3 Microcontroller Software
A microcontroller monitors three DIP switches to determine the operational mode of
the RTD board. A single “Mode” switch determines whether the board uses an internal
timebase or the digital input as a clock to step through the eight analog input
channels. When using the internal timebase, the other two DIP switches select one of
four clock periods.
Figure 2.10 – Scaled Analog Output for RTD Board
Analog Multiplexer
SA (1 of 8)
SB (1 of 8)
A0
A1
A2
DA
DB
NTC/RTD
Sourcing
Analog
Out
0-10V
12V
0.01 F
10
10
MAX4194
Instrumentation Amp
Rail-to-Rail
Gain Adjustable
Gain Adjust
DIP Switch Settings, S1
(overall gain)
50K
F
F
100K 100K F
F
100K 100K
4th Order Low Pass Filter
F
C
= 16Hz
Channel
Address
x10
Gain = 1 + 50K/Rg
100K
11.1K
MAX4194
x10
Rg
12V
5V
LMC6484
Quad Op Amp
Rail-to-Rail
x20
x30
x40
x50
x60
x70
x80
up
down
S1