G418 Isolator

RTD Input Field Configurable Isolator – G418

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Product Description

G418 Isolator

The Ultra SlimPak G418 Isolator is a DIN rail mount, RTD input signal conditioner with 1800VDC isolation between input, output and power. The field configurable input and output offers flexible, wide ranging capability for Platinum and Copper RTDs.

The input of the G418 Ultra SlimPak can be configured for any one of up to sixteen temperature ranges (see Tables 1 & 2). The output is linear to the RTD temperature input and can be set for either 0-5V, 0-10V, 0-1mA, 0-20mA or 4-20mA.

For an RTD and thermocouple input temperature transmitter with improved accuracy and stability, see Action I/Q model Q488. PC or DIP switch programmable.

Wide ranging, precision zero and span pots allow 50% adjustablity of offset and span turn-down within each of the sixteen switch selectable ranges. For example, the 0-500°F range could be offset and turned down to provide a 4-20mA signal representing 0-250°F (or 250-500°F).


The Ultra SlimPak G418 field configurable RTD input isolator is useful in eliminating ground loops and interfacing RTD sensors to data acquisition and control systems.

Three way isolation completely eliminates ground loops from any source. Isolation protects expensive SCADA systems from ground faults and significantly reduces the effect of high common mode voltages which are prevalent in many RTD applications.

The constant current RTD excitation circuitry uses the third lead of the RTD to sense and compensate for the RTD lead resistance, resulting in an accurate RTD temperature measurement.

High density DIN rail mounting offers an extremely compact solution for saving valuable panel space.

Diagnostic LED

The G418 is equipped with a dual function LED signal monitor. The green, front mounted LED indicates both DC power and input signal status. Active DC power is indicated by an illuminated LED. If the input signal is more than 110% of the full scale range, the LED will flash at 1Hz. Below -10%, the flash rate is 0.5Hz. If the LED flashes very fast, then the RTD input wires are open circuit. An 8Hz flash indicates that RTD input (+), terminal 41, is open circuit, or a 4Hz flash indicates that either RTD (-) or RTD Return, terminal 42 or 43, are open. The CAL LED is on under normal operating conditions. If the CAL LED is off when the unit is powered, consult the factory for assistance.


A major advantage of the G418 is its wide ranging capabilities and ease of configuration. The G418 has 16 input temperature range settings, six RTD type settings and five output range settings. Trim potentiometers allow 50% input zero and span adjustability within each of the 16 full scale input ranges.

Unless otherwise specified, the factory presets the Model G418 as follows:


Input: Pt100W
Range: -200 to 600°C
Output: 4-20mA


The DC power input accepts any DC source between 9 and 30V; typically a 12V or 24VDC source is used (see Accessories).

  1. After configuring the dip switches, connect the input to a calibrated RTD source or decade resistance box. Connect the output to the actual device load (or a load approximately equivalent to the actual device load value) and apply power.
  2. Set the calibrator to the desired minimum temperature and adjust the zero potentiometer for the desired minimum output.
  3. Set the calibrator to the desired maximum temperature and adjust the span potentiometer for the desired maximum output.
  4. Repeat steps 2 and 3, as necessary for best accuracy.


  • Sensor Types: Pt100, Pt500, Pt1000 (a: 0.00385W/W/°C or 0.00392W/W/°C); Cu10, Cu25, Cu100.
  • Sensor Connection: 3-wire.
  • Common Mode(Input to Ground): 1800VDC, max.
  • Zero Turn-Up: 50% of full scale range
  • Span Turn-Down: 50% of full scale range


Excitation Current

  • <2mA for Pt100, Pt500, Pt1000;
  • <5mA for Cu100;<10mA for Cu10, Cu25.


Leadwire Resistance

40% of base sensor resistance or 100W(whichever is less), max per lead.


Leadwire Effect

Less than 1% of the maximum input temperature span




Voltage Output

  • Output: 0-5V, 0-10V
  • Source Impedance: <10W
  • Drive: 10mA, max. (1KW, min @10V)


Current Output

  • Output: 0-1mA, 0-20mA, 4-20mA
  • Source Impedance: >100KW
  • Compliance:
    • 0-1mA; 7.5V, max.(7.5KW)
    • 0-20mA; 12V, max.(600W)
    • 4-20mA; 12V, max.(600W)


LED Diagnostics

  • Solid Green: power on
  • Flashing Green:
    • 0.5Hz input under range (<-10%)
    • 1.0Hz input over range (110%)
    • 4Hz input open circuit (terminal 41)
    • 8Hz input open circuit (terminal 42 or 43)
  • Yellow ON: = CAL OK

Accuracy Including Linearity, Hysteresis

±0.1% typical, ±0.2% max. of the maximum input temperature range configurable for the RTD type; @ 25°C ambient and 0W lead resistance.



±0.015% of the max. input temperature range for the RTD type per °C change in ambient temperature, max.


Response Time (10 to 90%)

200mSec., typical.


Common Mode Rejection

DC to 60Hz: 120dB



1800VDC between input, output and power.


ESD Susceptibility

Meets IEC801-2, Level 2 (4kV)


Humidity (Non-Condensing)

  • Operating: 15 to 95%( @ 45°C)
  • Soak: 90% for 24 hours( @ 65°C)


Temperature Range

  • Operating: 0 to 55°C ( 32 to 131°F)
  • Storage: -25 to 70°C (-13 to 158°F)


Wire Terminations

Screw terminals for 12-22 AWG



  • Consumption: 1.5W typical, 2.5 W Max.
  • Range: 9-30VDC



0.54 lbs


Agency Approvals

  • CSA certified per standard C22.2, No. 0-M91 and 142-M1987 (File No. LR42272)
  • UL recognized per standard UL508 (File No.E99775)
  • CE Conformance per EMC directive 89/336/EEC and low voltage 73/23/EEC.
Ordering Information
1. Specify: (model number) G418-0001
2. Accessories: (see Accessories)
3. Optional Custom Factory Calibration; specify C620 with desired input and output range.
All SlimPak “G” series modules will mount on standard TS32 (model MD02) or TS35 (model MD03) DIN rail. In addition, the following accessories are available:
HS01 Heat Sink
MD03 TS35 x 7.5 DIN rail
G905 24VDC Power Supply (0.5 Amp)
H910 24VDC Power Supply (1 Amp)
H915 24VDC Power Supply (2.1 Amp)
MB03 End Bracket for MD03
C664 I/O Descriptive Tags