3 | HX93A, HX93DA SERIES |
RH/Temperature Transmitter |
continued from page 1
HX15AV-W Wall mount “High Ambient Temperature” application RH/Temperature transmitter (dual 0 to 1 Vdc Output)
HX15AC-W Wall mount “High Ambient Temperature” application RH/Temperature transmitter (dual 4 to 20 mA Output)
HX15AV-D Duct mount “High Ambient Temperature” application RH/Temperature transmitter (dual 0 to 1 Vdc Output)
HX15AC-D Duct mount “High Ambient Temperature” application RH/Temperature transmitter (dual 4 to 20 mA Output)
3. 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 HX93A and the HX93DA Series the amount of current allowed to flow in the loop will vary depending on the relative humidity or temperature being measured by the sensor(s). 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 HX93A or HX93DA to function properly is found by using the following formula:
For HX93A
For HX93DA
Rmax = (power supply voltage – 6 volts) ÷ .02 amps
EXAMPLE: (When using a 24 Vdc power supply).
Rmax = (24 – 6) ÷ .02 amps = 900 ohms max loop resistance Rmax = (power supply voltage – 12 volts) ÷ .02 amps
EXAMPLE: (When using a 24 Vdc power supply).
Rmax = (24 – 12) ÷ .02 amps = 600 ohms max loop resistance |
+ | 23°C | – |
DPi8 Panel Meter |
TB2 | | |
+ | 24V | – |
| |
| PSU-93 | |
TB1 | | |
+ | 45%RH | – |
2 | Figure 1 - Basic Transmitter Set-up With Current Loop Output |
