HDR200: High Temperature and High Pressure Dew Point and Relative Humi

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HDR200: High Temperature and High Pressure Dew Point and Relative Humidity Transmitter

This video highlights the key functionality and how to get started with the HDR200, a dew point and relative humidity transmitter that can be used in high temperature and pressure applications.

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The HDR200 is an indicator and 4-20ma loop powered transmitter used for measuring moisture content in air and other gases. It’s reliable, accurate and easy to use but what makes it unique is that its probe can be mounted and operate in gas temperatures up to 200°C with pressures up to 750PSI.

The HDR200 can be configured by the user for either dew point temperature measurement or relative humidity measurement. Changing from dewpoint to humidity is simple and only requires changing an internal dipswitch, however, for the user’s convenience IOThrifty sells the HDR200 preconfigured for either dew point temperature measurement under the part number HD200 or humidity measurement as the HR200. Later in this video we’ll show how easy it is to switch from one measurement to the other. For the purpose of this video, we’ll refer to the device as the HDR200, but the actual part number used when ordering would be either HD200 or HR200.

The HDR200 includes a stainless-steel probe, a compression fitting for mounting the probe and an electronics unit that provides display of the measurement. The electronics unit also has a 4-20 milliamp output that is a retransmission of either the humidity or dewpoint temperature. The HDR200 also comes with a NIST traceable calibration certificate.

The measurement capability of the probe is what really makes the HDR200 an exceptional device. It has the ability to be mounted in environments with temperatures up to 200°C and pressures up to 750 PSI. Very few humidity or dew point measurement instruments on the market can handle that level of temperature and pressure. This makes the HDR200 a great choice for applications involving compressed air, dryers, and environmental chambers.

The probe length is six- and one-half inches, but the compression fitting allows the probe to be extended to different lengths into the process by sliding the probe through the fitting until the desired length is reached. Once the desired length is reached you can tighten the compression fitting on to the probe locking the probe in place and creating a pressure tight seal.

The probe is connected to the electronics unit by a cable one meter in length. As a special order, we can provide the HDR200 with a longer cable length up to 25 ft. Please contact IOThrifty for more details.

The electronics unit has a dual display. When configured for dew point temperature , the display will show both dew point temperature and temperature. When configured for humidity, the display will show both humidity and temperature. We’ll power this one up in a few moments to show the display.

The HDR200 is also a two-wire loop powered transmitter which means power and transmitted signal travel through the same two wires. We’ll show exactly how this works later in this video but let’s start by powering up this unit to show the display.

The red wire is positive and the black wire is the negative. Although the standard wire length is 12 inches, the wire can be extended by the user just by splicing additional lengths of standard signal wire.

The HDR200 is powered by 12 to 28 volts dc power. For this demonstration we’ll use an adjustable power supply which allows me to make a quick temporary connection using clip leads, but for a more permanent installation IOThrifty also sells low-cost power supplies like the PSJ-R which converts AC to DC voltage, plugs into a standard AC outlet and provides screw terminal connections for its DC voltage output. It’s a good low cost accessory to purchase along with a HDR200 if you don’t have dc power readily available.

I’m now connecting the HDR200 to my power supply which is set to put out 24Vdc. As soon as the power is applied you can see the HDR200 turns on and displays both a dew point temperature as well as temperature.

Since this is an HD200 it shows dew point temperature. If it was configured as an HR200 it would display humidity instead of dew point temperature. We’ll show how to switch it over in a few minutes.

If you are using this for display purposes only, there is nothing else that needs to be done but the HDR200 also has an analog output that retransmits the measured value as a 4-20ma signal. When the display is set for humidity, the 4-20mA output will equal 0 to-100% relative humidity. If the display is set for dewpoint temperature, the 4-20mA output will have a default factory scaling of minus 60 to 40°C dew point temperature. The full range of the HD200 is minus 60 to 100 degrees C which is the range of the display. If you would like the analog output scaled differently please let us know at the time of ordering and we’ll be happy to scale it to your specified range.

I’m now going to demonstrate the 4-20 mA output. As I mentioned earlier the 4-20mA output is a two wire loop output in which the power and signal travel along the same two wires. Here is a simple wiring diagram showing the HDR200 connected to a power supply and an instrument to measure the 4-20mA signal.

The circle with the A inside it represents a milliamp meter which could be a panel meter, a controller, a data logger, or any other instrument that can read a 4-20mA signal.

In this diagram the milliamp meter is wired between the negative of the HDR200 and the negative of the power supply. 

We could also wire it between the positive connections as shown in this diagram.

For this next demonstration we’re going connect the HDR200 to a N1540 panel meter. The N1540 is a low-cost panel meter that can accept signals from thermocouples, RTDs and other sensors or devices with a voltage or 4-20mA output. I’ve chosen the N1540 for this demonstration since it also provides 24 volts power which we’ll use to power the HDR200. In this demonstration the N1540 is located right next to the HDR200 but in a more practical application the N1540 could be located hundreds of feet away. The HDR200 comes with three feet of cable but that can be extended in the field with just ordinary copper wire.

This diagram shows the wiring between the N1540 and HDR200. Because the N1540 provides 24Vdc power we no longer need the power supply we used in our last demonstration. Here we now show the N1540 and HDR200 working together.

You may notice that the dew point temperature is lower than the last time we powered up the HDR200. That is because this portion of the video was recorded on a different day. Prior to connecting the two devices, I configured the N1540 for a 4-20mA input and set the scaling for 4 millimps equal to minus 60 and 20 milliamps equal to 40°C to match the default scaled output of the HD200.

I mentioned a few times earlier in this video that several of the configuration options of the HDR200 could be set by internal dips switches. Here you can see I removed the four screws holding the HDR200 cover in place to show the location of the dip switches. The red switch block actually has 2 switches, the one on the left is for changing the reading from dew point temperature to humidity and vice versa. The switch on the right is for setting the temperature units of the display to either degrees F or degrees C. This will affect both the temperature and dew point temperature. I am going to change the leftmost dip switch and after applying power you can see that my display which was previously showing dew point temperature is now showing relative humidity.

If I now change the switch on the right. My temperature reading will change from degrees C to degrees F.

Before concluding this video I wanted to mention two additional items.

The first is that we also offer a version of the HDR200 with an M12 connector instead of the wire leads that are on the the unit that we’ve been demonstrating. The M12 connector makes it easy to quickly connect or disconnect the HDR200 but it also provides access to not only the 4-20mA loop but also RS232 communications. With RS232 you can read dew point temperature, relative humidity and temperature from a computer or PLC.

And the final important point I want to mention is that that although the HDR200 can read up to 200°C it must be a non-condensing environment since condensation can damage the sensor. However, if you have a condensing environment IOThrifty may have a solution for you. Please contact us and we’ll be happy to discuss your application.

Thank you for watching this video. Feel free to reach out to us with any questions or comments.