RTD Transmitter Installation Instructions
RTDT Series Models
RTDT-96091N
Revised 01-01
Section 10
00-02-0849
Description
The Murphy RTD transmitter is designed to accept a signal from an RTD sensing
element, and to provide a linearized 4 to 20 mA output current. The output cur-
rent is directly proportional to the temperature of the RTD temperature sensor.
Since the temperature is converted to a current signal, voltage drops in the power
supply leads to the transmitter have no effect on the integrity of the signal. As long
as the transmitter has sufficient DC voltage at its terminals, it will produce a cur-
rent linearly proportional to temperature. This means that the transmitter may be
remote mounted but should be near the sensor, reducing the effects of noise and
minimizing errors due to long leads on the RTD sensor. The RTD instruments
have screw terminal connections and accept 2 or 3 wire RTD's* . They include
high resolution, 24-turn zero and span potentiometers and each unit is calibrat-
ed after a minimum of 48 hours burn-in and checkout time.
*
Three wire RTD's compensate for leadwire resistance.
Specifications
Sensor Input:
Platinum RTD 100 ohms
Output Span:
4 to 20 mA
Loop Power Supply Voltage:
Typically 24 VDC; when using Loop Resistance
Graph 13 – 40 VDC.
Temperature Span:
50°F (28°C) minimum
;
1000°F (556°C) maximum
Calibrated Accuracy:
0.1 %
Conformity:
0.1 % of Span
Ranges:
-60 to 140°F; 0 to 400°F
Ambient Temperature Limits:
-30 to 165°F (-34 to 74°C)
Power Supply Effect:
0.001% volt
Current:
3.4 mA
minimum;
30 mA
maximum.
Upscale Burnout:
Standard
Reversed Polarity Protection:
Standard
Nominal Zero and Span Adjustments:
±10%
Connections:
Screw Terminal
Power Supply
Transmitters are designed for a nominal 24 VDC power supply. They will
operate with a 13 to 40 VDC supply at the transmitter power supply terminals.
Use the following formulas to determine maximum resistive loading (RL)
allowed for the power supply used, or to determine minimum supply voltage (V)
required for fixing resistive loads. Formulas assume a max. current of 20 mA.
NOTE:
Devices such as Murphy’s EMS Series controllers, 400 and 500 Series PLC
controllers, and the RMU16 have 250 ohms resistors that add to the resistve loading.
Power Supply Voltage
Resistive Load
(Minimum)
(Maximum)
V= (0.02 A x RL) +13 V
RL=(V - 13) /0.02
Example:
Example:
550 ohm load
24 VDC power supply
V=0.02 x 550 +13
RL=(24 V - 13 V) /0.02
V= 24 VDC minimum power supply
RL=550 ohm maximum
Wiring
The terminal strip on the transmitter accepts 14 to 22 gauge wires. Copper wire is
to be used since special compensation wire is not required. Route all transmitter
wiring in separate conduit to isolate it from high voltage or high current carrying
lines. It is also recommended that shielded wire be used for the 4-20 mA signal.
Please read the following information before installing
.
A visual inspection of this product for damage during shipping is recommended
before mounting. It is your responsibility to have a qualified person install this unit and make sure it conforms to NEC and local codes.
GENERAL INFORMATION
WARNING
BEFORE BEGINNING INSTALLATION OF THIS MURPHY PRODUCT
✔
Disconnect all electrical power to the machine.
✔
Make sure the machine cannot operate during installation.
✔
Follow all safety warnings of the machine manufacturer.
✔
Read and follow all installation instructions.
ZERO
Rlin
SPAN
NOTE
NOTE: Slot accepts 6-32 screw
0.138 in. (3.50 mm)
1.080 in.
(27.43 mm)
0.14 in.
(3.55 mm)
2.20 in. (55.8 mm) Max.
0.67 in.
(17.1 mm)
1.50 in. (38.1 mm) Max.
ZERO
Rlin
SPAN
Indicator
Controller
RTD
White
DC Power Supply
+
+
--
--
Red
Red
Dimensions
CAUTION:
Do Not connect power to the RTD input. Do Not
connect power to the RTD itself. Do Not use AC line power.
Loop Resistance Graph
Supply voltage for the RTDT must be within 13-40 VDC. The figure below shows
the minimum supply voltage (VDC) required for a given load resistance (RL).
1500
1000
500
250
10
20
30
40
50
13
18
0
Under
Voltage
Area
Operating
Area
18V, 250
Ω
23V, 500
Ω
33V,
1000
Ω
Over
Voltage
Area
Total Load Resistance (RL)
*
Power Supply Voltage (VDC)
*
NOTE: Cable resistance effect included in RL.
