RT318
8-channel RTD input
Type
RT318
Category
RTD ( Resistance Temperature Detector ) input
Resistance temperature
detectors
Pt100
Measuring method
Load current
Three-wire system
1 mA
-50 to +270 C (-58 to +518 F)
Temperature measurement
range
°
°
°
°
Converted data
800 to 4000
Input channel
Insulation
8 channels / module
Photo-coupler insulation (not isolated between the channels)
400 ms / 8 channels
Conversion rate
Resolution
12 bits / 0.025 % ( 0.1 C / count )
°
Wire resistance correction
range
Within 4
Ω
0.3 (at 25 C)
Overall accuracy
Tepaerature drift
±
%
°
100 ppm / C
±
°
Internal current consumption 5 Vdc, 600 mA or less
10 M (500 Vdc)
Insulation resistance
Withstand voltage
Weight
Ω
500 Vac, 1 minutes ( between internal and external circuits)
500 g
Internal circuit
Current source
1 mA
1 mA
AMP
1A
1B
1C
1G
ADC
PC
PC
CH1
CH8
Rref
Rref
Wire break
detection
AG
5 Vdc
8A
8B
8C
8G
+15V
-15V
DC/DC
0V
AG
PC : Photo-coupler
1
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RT318
(1) Status indicator LEDs (PWR/FLT/RUN)
1) PWR
PWR will be lit in normal state of analog power supply, and will not be lit in abnormal state.
2) FLT
FLT will be lit if an error has occurred in the module.
3) RUN
RUN will be lit in normal state of the module, and will not be lit in abnormal state.
Name
PWR
FLT
Lit ●
Not lit ○
abnormal state
Normal state
abnormal state
Normal state
Error occurred
Normal state
(1)
(2)
RUN
(2) Unused terminals
(3) RTD input terminals (1A/1B/1C/1G to 8A/8B/8C/8G)
These terminals will be connected with external RTD signals.
(3)
3
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RT318
How to wire
Shielded twisted cable
Internal circuit side
nA
RTD
(Pt100)
nB
nC
nG
AG
FG
RTD
:
Resistance
Detector
Temperature
n
AG
:
:
Channel number
Analog ground
FG : Frame ground
If measurement values are unstable due to noise influences, change the grounding for
the shield in the following order for stable measurement.
Shielded twisted cable
Internal circuit side
nA
(1)
RTD
nB
nC
nG
(Pt100)
AG
FG
(2)
Shielded twisted cable
Internal circuit side
nA
RTD
(Pt100)
nB
nC
nG
AG
FG
Shielded twisted cable
Internal circuit side
nA
(3)
RTD
nB
nC
nG
(Pt100)
AG
FG
Supplementary
To minimize the influences of the wire resistance, be sure the wire
length to be same of each cable from the terminal nA , nB or nC to
RTD.
4
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