G108 Alarm

DC Input Limit Alarm Ultra SlimPak® – G108

Product Description

G108 Alarm

The Ultra SlimPak G108 Alarm is a DIN rail mount, DC voltage or current input limit alarm with dual setpoints and two contact closure outputs. The field configurable input and alarm functions offer flexible setpoint capability. Input voltage spans from 10mV to 200V and input current spans from 1mA to 100mA can be field configured. Bipolar inputs are also accepted.

The G108 is configurable as a single or dual setpoint alarm, with HI or LO trips and failsafe or non-failsafe operation. Also included are adjustable deadbands (0.25 to 5% of full scale input) for each setpoint, a 24VDC voltage source (isolated from line power) for transducer excitation, and a flexible DC power supply which accepts any voltage between 9 and 30VDC.

Diagnostic LEDs

The G108 is equipped with three front panel LEDs. The green LED is a dual function LED labeled INPUT. This LED indicates line power and input signal status. Active DC power is indicated by an illuminated LED. If this LED is off, check DC power and wiring connection. If the input signal is more than 110% of the full scale range, the LED will flash at 8 Hz. Below 0%, the flash rate is 4 Hz.

Two red LEDs indicate the relay state for each setpoint. An illuminated red LED indicates the tripped condition.


The G108 is equipped with two SPDT (form C) relays, rated at 120VAC or 28VDC at 5 amperes. Each of these relays is independently controlled by the field configurable setpoint and deadband.


The field configurable G108 limit alarm setpoints can be configured for HI or LO, failsafe or non-failsafe operation. Each of the setpoints has a respective HI or LO deadband. In a tripped condition, the setpoint is exceeded and the appropriate red LED will illuminate. The trip will reset only when the process falls below the HI deadband or rises above the low deadband (see Figure 1). For proper deadband operation, the HI setpoint must always be set above the LO setpoint. In failsafe operation, the relay is energized when the process is below the HI setpoint or above the LO setpoint (opposite for non-failsafe). In the failsafe mode, a power failure results in an alarm state output.

wv108 fig 1
Figure 1: Limit alarm operation and effect of deadband.
Dynamic Deadband

LSI circuitry in the G108 prevents false trips by repeatedly sampling the input. The input must remain beyond the setpoint for 100 milliseconds, uninterrupted, to qualify as a valid trip condition. Likewise, the input must fall outside the deadband and remain there for 100 milliseconds to return the alarm to an untripped condition. This effectively results in a “dynamic deadband” —based on time— in addition to the normal deadband.


Unless otherwise specified, the factory presets the Model G108 as follows:

Input: Current
Range: 0-20mA
Output: Dual, SPDT
Trip: A:HI, B:LO
Failsafe: No
Deadband: A, B: 0.25%


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

For other I/O ranges, refer to Table 1 and Figure 4. Reconfigure switch SW1 for the desired input type, range and function.

  • With DC power off, set position 9 and 10 of SW1 for current or voltage (see Table 1).
  • Set position 1 through position 4 of input range switch “SW1” for the desired input range (see Table 1).
  • Set position 5 of input range switch “SW1” to ON for unipolar (e.g. zero based, 0-20mA) range or OFF for bipolar (e.g. -100% offset, -20 to 20mA) range (see Figure 4).
  • Set position 6 and 7 of input range switch “SW1” to ON for a HI trip setpoint or OFF for a LO trip setpoint (see Figure 4).
  • Set position 8 of input range switch “SW1” to ON for non-failsafe operation or OFF for failsafe operation (e.g. alarm trips upon power failure).
g108 table
Table 1: G108 Input Range Settings
WV108 fig2
Figure 2: DC Inductive Loads
WV108 fig3
Figure 3: AC Inductive Loads
  • After configuring the DIP switches, connect the input to a calibrated DC source and apply power. Refer to the terminal wiring (Figure 7).
  • Setpoint: set deadband at its minimum (fully counter clockwise) before adjusting the setpoint. With the desired trip voltage or current input applied, adjust setpoint until the relay trips. For HI trip calibration, start with the setpoint above the desired trip (full clockwise). For LO trip calibration, start below the desired trip (full counter clockwise).
  • Deadband: Set deadband to its minimum (fully counter clockwise). Set the setpoint to desired trip. Adjust voltage/current input until relay trips. Readjust deadband to 5% (fully clockwise). Set voltage/current input signal to desired deadband position. Slowly adjust deadband until relay untrips.
G108 fig4
Figure 4: G108 Input Range/Function Selection (SW1) Factory Default Settings
Voltage Input
  • Range: 10mV to +200V
  • Impedance: >100ohms
  • Overvoltage:200V rms, max.
Current Input
  • Range: 1mA to +100mA
  • Impedance: 20, typical
  • Overcurrent: 170mA rms, max.
  • Overvoltage: 60VDC (protected by self resetting fuse)
  • Common Mode (Input to Ground): 1800VDC, max.
LED Indicators

Input Range (Green)

  • >110% input: 8Hz flash
  • <0% input: 4Hz flash
Setpoint (Red)

Tripped: Solid red

Safe: Off

Limit Differentials (Deadbands)
  • >50mV/5mA: 0.25% to 5% of span
  • <50mV/5mA: 1% to 5% of span
Response Time
  • Dynamic Deadband: Relay status will change when proper setpoint/process condition exists for 100msec.
  • Normal Mode (analog filtering): <250mSec, (10-90%)
  • Effectivity: Setpoints are adjustable over 100% of the selected input span.
  • Repeatability (constant temp.):
    • >50mV/5mA: 0.1% of full scale
    • <50mV/5mA: 0.2% of full scale

Temperature: +0.05% of full scale/°C, max.

Excitation Voltage

24VDC, 20mA, maximum


DC to 60Hz: 120dB


1800VDC between contacts, input and power

EMC Compliance (CE Mark)
  • Emmissions: EN50081-1
  • Immunity: EN50082-2
  • Safety:EN50178
Humidity (Non-Condensing)
  • Operating: 15 to 95% (@45°C)
  • Soak: 90% for 24hours (@65°C)
Temp Range
  • Operating:0 to 55°C (32 to 131°F)
  • Storage:-25 to 70°C (-13 to 158°F)
Power  Consumption:

1.5W typical, 2.5W max.

Supply Range:

9 to 30VDC, inverter isolated

Relay Contacts
  • 2 SPDT (2 form C) Relays
  • 1 Relay per setpoint
Current Rating (resistive)
  • 120VAC: 5A
  • 240VAC: 2A
  • 28VDC: 5A
  • Material: Gold flash over silver alloy
  • Electrical Life: 10^5 operations at rated load
  • Mechanical Life: 10^7 operations
Wire Terminations

Screw terminations for 12-22 AWG



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 (Input < 75VDC, only).
Ordering Information
1. Specify: (model number) G108-0001
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 Heatsink (vertical rail applications)
MD03 TS35 x 7.5 DIN rail
WV905 24VDC Power Supply (0.5A)
H910 24VDC Power Supply (1Amp)
H915 24VDC Power Supply (2.3 Amp)
MB03 End Bracket for MD03
C664 I/O Descriptive Tags
C006 Shunt Resistor (0.1, 5A max.)