EWS-RH
Relative Humidity/Temperature Transmitter
2
Additional EWS Series Models Available
Model
Description
EWS-TC-(*)
Wall mount thermocouple sensor
(* = insert type,J, K, T, E)
EWS-RTD
Wall mount RTD sensor (100 Pt., .00385)
EWS-TX
Wall mount solid state temperature transmitter
EWS-BP-A
Wall mount barometric pressure transmitter
Theory of Operation
A 4-20 mA loop is a series loop in which a transmitter will vary the
current flow depending on the input to the transmitter. In the EWS-RH
the amount of current allowed to flow in the loop will vary depending
on the relative humidity or temperature being measured by the sensor.
Some advantages of a current output over a voltage output is that the
signal measured is less susceptible to electrical noise interference and
the loop can support more than one measuring instrument as long as
the maximum loop resistance is not exceeded.
A typical application utilizing a current loop will normally consist of a
power supply, the transmitter and a meter, recorder or controller to
measure the current flow. The loop resistance in the sum of the
measuring instruments and wire used. The maximum allowable loop
resistance for the EWS-RH to function properly is found by using the
following formula:
Rmax = (power supply voltage - 8 volts)/.02 amps
For applications that require a voltage output signal the EWS-RH has a
built-in 250 Ohm shunt resistor that will convert the transmitters
output to a 1-5 Vdc signal when wired correctly. See "
Transmitter Wiring
Examples
" in this manual.
Recommended Accessories
Power Supply, OMEGA
®
Part No.: PSU-93
Shielded 4-conductor cable, OMEGA
®
Part No.: TX4-100
Conduit Box Mounting Kit, OMEGA
®
Part No.: EWS-MB
