For years, the HMP60 Temperature and Humidity sensor was used primarily with DI-710 series instruments. The DI-710 was (and still is) able to provide the necessary supply voltage (5 to 28VDC) and acquire both 0 to 2.5VDC outputs (-40 to 60°C and 0-100% RH). With the recent addition of the DI-8B43 DC Transducer Amplifier to our selection of signal condition modules, the HMP60 can now be used with DI-718B, DI-718Bx and DI-788 series instruments, as well.
The DI-8B43 includes a 10V supply and a single analog voltage input (±1 to ±5). Used in combination with an additional analog voltage module (a DI-8B31 or DI-8B41, for example), you can power the HMP60 and acquire both temperature and relative humidity.
In this example, we’ll use a DI-8B43-05 and a DI-8B41-02 module, housed inside of a DI-718B. Connections are made as follows:
Note that the ground wire must be connected to the negative excitation terminal (Ex-) of the DI-8B43, in addition to the negative input terminal (In-) of both the DI-8B43 and the DI-8B41. This can be done using a jumper wire. In addition, a small load must be placed across the excitation output of the DI-8B43 module (a 1kΩ resistor in this case).
Scaling to Display Temperature and Humidity
To display engineering units (C and %RH) we’ll use the ‘Engineering Unit Settings’ option in WinDaq.
Begin by select channel 1 and choosing ‘Engineering Unit Settings” from the ‘Edit’ pull-down menu.
Since we know that the HMP60 outputs 2.5V at 60°C, we’ll enter 2.5 for Upper Level Volts and 60 for Upper Level EU. We’ll enter 0 for Low Level Volts and -40 for Lower Level EU. For EU Tag, enter “C”.
With the humidity output connected to channel 2, we’ll enter 2.5 for Upper Level Volts, 100 for Upper Level EU. We’ll enter 0 for Low Level Volts and 0 for Low Level EU. For EU Tag, enter “%RH”.
As you can see, WinDaq now displays temperature in degrees C and relative humidity in %RH.