Humidity and temperature sensors with ATEX certificate for use in explosion hazardous areas and locations with inflammable dust. Area of application 1G, 1/2G and 2D. The sensors consist of a robust aluminium die-cast housing (transmitter part) with a mounted sensor part with sintered filter (both made of stainless steel).
MELA®-Humidity/-temperature sensors in these series are used to measure relative humidity or temperature or relative humidity and temperature in air and other non-aggressive gases in explosion hazardous arears and in locations with inflammable dust.
The sensors comprise a sensor part with a sintered filter mounted on a robust aluminium die-cast housing (transmitter part), both made of stainless steel.
Connection to a non-intrinsically safe electric circuit for humidity (F*C3.Ex/8) and for temperature sensors (T*C3.Ex/8) is achieved with a 1-channel transmitter power supply unit and for the combined humidity and temperature sensors(K*C3.Ex/8) either with a 2-channel or with two 1-channel transmitter power supply units with galvanic isolation between input-/output circuits and power supply.
If used as intended and if the assembly instructions and ambient conditions have been taken into consideration, then no running maintenance is necessary.
In order to arrange a simple test of the functionality of the sensor on the site, we recommend the MELA®-humidity standard type ZE 31/1 with the additional adapter type ZE 33 (product information no. F 5.2). Dust does not damage the sensor but it negatively affects its dynamic behaviour. The sintered filter can be carefully unscrewed and washed out if too much dust accumulates.
Loose dirt can also be removed from the measuring element by blowing or carefully flushing with distilled water. The sintered filter should be in an absolutely dry condition when it is screwed on again in order to avoid measurement errors. It is important not to touch the highly sensitive sensor element in the process. The screw connection on the sintered filter has to be firmly tightened.
MELA®-humidity/temperature sensors should be installed in a location which is representative for measuring the environmental conditions.
Connection to a non-intrinsically safe power circuit is achieved by using either one or two transmitter power supply units (U0, I0, P0) according to the connection diagram.
To verify the intrinsic safety in a simple, intrinsically safe electric circuit, the values of the intrinsically safe equipment (Ui, Ii, Pi, Ci and Li), of the corresponding electrical equipment (transmitter power supply U0, I0, P0, C0 and L0) and of the cable (C and L) need to be compared to ensure that the intrinsically safe equipment is not overloaded and the energy stores L and C are not greater than L0 and C0 of the corresponding equipment.
For the performance, even with a trapezoidal characteristic curve, the value P0 of the transmitter power supply is to be used. Basically, the max. cable length only depends on C0 of the transmitter power supply and on the type of cable used, as circuit engineering measures have been taken to ensure that the internal capacity of the sensor does not impact externally.
We recommend the cable type NF14 and a max. cable length of 200m. During installation, the additional requirements for the protection type „i“ – intrinsically safe according to DIN EN 60079-14, must be complied with.
Only fixed cables and electric lines may be inserted into the cable gland. After connecting it up, the housing must be sealed tightly again. To do so, the screws in the cover must be tightened with a torque of 1.5 to 2.0 NM. The intrinsically safe humidity and temperature sensors (type of protection „ia“) can also be used as class 1 equipment.
If you do this, make sure you only use assembly kit ZA40 when attaching the sensor to a partition barrier.