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GWZ S4.1 200x200

GWZ-S2.1 / GWZ-S4.1

The freely programmable, self-regulating limit monitors are used for indicating the concentration of gases and vapors.

When exceeding or falling below a certain threshold, an alarm is triggered.

Similarly, via potential-free relay output, it is possible to activate devices, such as: magnetic valves, fans and acoustic transmitters.

The unit is available for wall mounting free to choose 24 V DC or 230 V AC power supply.

Connection with up to four sensors and two digital inputs

Depending on the configuration up to 4 sensors out of the product range can be connected to the 4..20 mA interface. The sensors are supplied via this device with 24 V DC. There is also a digital input for to wire a digital signal contact (e.g. pressure, water level) and a digital input for the external horn reset.

Relay outputs with test function for alarm, horn and malfunction

The limit monitor has 4 potential-free relay outputs, which are configured as follows:

  • Up to 4 alarm relay: The relay contacts report an exceeding or falling below the threshold limits. So, for example, they can visually and acoustically trigger pre and main alarm or start-and turn off a fan again. The alarm outputs are available with hysteresis, latching or latching prematurely acknowledged. The alarm relay can be assigned a time function (minimum pulse time, maximum pulse time, delayed on/off).
  • 1 x Horn relay to control a horn
  • 1 x fault alarm relay: While the limit monitor keeps a watch on cable break, short circuit, and electronic failure, the fault message relay system displays malfunctions.
    A test function allows the verification of the output relay.

Control unit with display and status indicator

Via an alpha-numeric display the concentration values of the connected sensors are shown on a rolling basis. Additional status LEDs display information about the operating status, malfunction, horn and alarms.

Configurable on the device or via PC interface

The device can be either configured directly via button and display or being connected by an RS232 interface to a PC. By using the configuration software the device can be easily configured via PC.
At the limit monitor the following parameters and settings can be programmed for each sensor individually (via button or PC interface):
The limits, the final measuring range value, the unit of measure (LEL, ppm, vol%, °C, etc.), alarms (made either when exceeding or falling below the limit) and alarm output (optionally being stored, not stored or carried as an impulse).

Suitable for wall mounting

The limit monitor is available in a waterproof housing (IP65) for wall mounting free to choose between 24 V DC and 230 V AC supply voltage.

Configurable data logger

With the configurable internal data logger the data of each sensor connected can be recorded and be read again via the PC interface.

Self-monitoring with fault detection for cable break, short circuit and power failure

The device is self- monitoring the wiring of the sensor. It detects wire break and short circuit while triggering a fault message. The malfunction alarm relay is designed fail-safe, means, in case of failure power supply is cut off (closed-circuit principle) and a power failure can thus be detected.

"Inhibit" mode of operation

The "Inhibit" feature allows freezing the relay status for more than 20 minutes. This prevents from triggering the alarm during maintenance.


The limit monitors meet the following directives and standards:

  • EMC Directive 2014/30/EC and the standards DIN EN 50270:2007-05, DIN EN 61000-6-2:2006-03 and DIN EN 61000-6-3:2007-09
  • Low Voltage Directive 2014/35/EC and the standard EN 61010-1:2011.

Maintenance and Service

The device itself is maintenance free. We recommend regular maintenance for the connected sensors. For this purpose we offer a test gas suitcase or you send the probes to us. Please contact our service center.

Product NameProduct FeaturesProduct Code
GWZ-S2.1 2 Measuring channels 4-20 mA
24 V DC
2 Measuring channels 4-20mA
230 V AC
GWZ-S4.1 4 Measuring channels 4-20 mA
24 V DC
4 Measuring channels 4-20 mA
230 V AC


Power supply voltage 24VDC oder 230VAC
power rating approx. 13 W (without sensors)
Ambient temperature -10°C to +50°C  
Permissible humidity 15% to 95% relative humidity non-condensing
Housing plastic, grey wall mounted
protection class IP 65
weight approx. 1,000 g
dimensions (W x H x D) 240 x 120 x 190 mm


Port A (measuring system 1) terminal 1 (out) 24 V DC ± 5%
terminal 2 (in) 4–20 mA; maximum ohmic resistance 370 Ω
terminal 3 (out) 0 V
Port B (measuring system 2) terminal 4 (out) 24 V DC ± 5%
terminal 5 (in) 4–20 mA; maximum ohmic resistance 370 Ω
terminal 6 (out) 0 V
Port C (measuring system 3)
(GWZ-S4.1 only)
terminal 19 (out) 24 V DC ± 5%
terminal 20 (in) 4–20 mA; maximum ohmic resistance 370 Ω
terminal 21 (out) 0 V
Port D (measuring system 4)
(GWZ-S4.1 only)
terminal 22 (out) 24 V DC ± 5%
terminal 23 (in) 4–20 mA; maximum ohmic resistance 370 Ω
terminal 24 (out) 0 V
Relay malfunction terminal 7 operating contact
terminal 8 root
terminal 9 rest contact
non-operating state failure
Relay alarm 2 terminal 10 operating contact
terminal 11 root
terminal 12 rest contact
rest contact alarm 2
Relay alarm 1 terminal 13 operating contact
terminal 14 root
terminal 15 rest contact
rest contact alarm 1
Relay horn terminal 16 operating contact
terminal 17 root
terminal 18 rest contact
non-operating state horn off
External power supply terminal N, PE, L  
Relay potential free changeovers load 250 V AC, 1 A
powered off system all relay at rest
Digital interface X1 RS 232 for configuration
Digital input external horn reset or digital alarm input
terminal + 24 V DC ± 5%
terminal D high = 24 V, low = 0 V
terminal HU high = 24 V, low = 0 V
terminal GND 0 V

Display and Operation

Optical display yellow LED Error error message
green LED Power operation
red LED Horn audible alarm
red LEDs
A, B, C, D
alarm over channel A, B, C, D
(channel C, D for GWZ-S4.1 only)
Controls button F1 and F2 function keys
reset button horn reset, alarm reset
Alpha-numeric display measuring plane concentration, status, fault, threshold exceeded
parameter display display of measurement ranges, limits, alarm groups
special functions functional test of the relay, Inhibit mode of operation

Pin assignment


In the product version GWZ-S2.1, the terminals 19 to 24 are not present. All relays are marked in non-operating state.

Product NameProduct FeaturesProduct Code
Configurations-Set Set consisting of:
- CD with configuration software
- connector cable for PC (data cable)
Signal horn-set
230 V AC
Set consisting of:
- signal horn, orange, 230V
- warning light, red
- filament lamp 230V
Signal horn-set
24 V DC
Set consisting of:
- signal horn, orange, 24V
- warning light, red
- filament lamp 24V
USB-serial adapter Adapter for connection of RS232 devices plug into the USB port of a PC Z0A0-H0001