Apps
Measuring instruments with Wika inductive electrical contacts can be used in the operating rooms of Zones 1 and 2 for explosion risk. When in use, these meters must be powered by a suitable and certified control unit such as the 904.15 control unit.
In addition to Ex hazardous areas, Wika's inductive electrical contacts are used primarily for applications that require frequent switching and have high safety requirements for electrical contacts. Because the electrical contacts work in a liquid-filled environment, they can be used in special work environments. Typical applications include the chemical industry, the petrochemical industry, and nuclear facilities.

Features
Type 904.28 is suitable for equipment with 1 inductive electrical contact, through 1 x SPDT (single pole double throw) output
904.29 is suitable for devices with 2 inductive electrical contacts, output through 2 x SPDT (single pole double throw)
Type 904.30 is suitable for safety equipment (SN or S1N) with 1 inductive electrical contact, can pass 1 safety relay, 1 pulse or 1 passive electronic output
Explosion-proof type: EEx-ia IIc
rated electrical power: AC 250 V / 2 A / 500 VA (type 904.30 is 1 A)
On and off delay: 20 ms
Environmental temperature: -20 … +60 °C
Protection rating: IP20
Control unit with DC 20 … 30 V power supply
904.31 - 1 relay output
904.32 - 2 relay output
904.33 - 1 safety relay output

Description
Weika's devices with inductive electrical contacts are non-contact devices. The device has an exciter on the nominal value pointer. The exciter includes a fully sealed electronic circuit and a mechanical structure with movable control vanes. The control blade moves as the meter pointer turns (nominal value pointer).
The exciter is powered by a DC power supply. If the control vanes move into the gap of the exciter, the internal resistance of the exciter increases (ie, the exciter is active or the resistance is increased). This causes the current to change, and the current change can be used as an input signal to the switching amplifier in the control device.