Hydrogen peroxide vapor probes and analog connectivity

In this video blog, product engineer Joni Partanen demonstrates how to connect and test the HPP270 vaporized hydrogen peroxide probe when it is used in analog output mode. The HPP270 probes can also be connected digitally and there is a separate video on that topic. In this demonstration, we focus on connecting the probe to the control system by using analog mA-outputs.
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Edited transcript
I have here an HPP270 probe for measuring vaporized hydrogen peroxide in bio-decontamination processes. It measures vH2O2 concentration and humidity as relative saturation. There are fundamentally two different ways to connect this probe to your control or data acquisition system. You can connect it as a standalone probe or use a Vaisala host device (Indigo transmitters), which provides additional features.

 

The standalone probe has two analog outputs, or it connects with Modbus RTU digital communication (see video on this method). If you decide to use Vaisala’s Indigo200 or Indigo500 series transmitters, you will get additional features such as local display, more analog outputs, and more options for digital communication options.

This is a demonstration of how to use an HPP270 as a standalone probe using analog outputs. The probe comes with two analog outputs. The first probe measures vaporized hydrogen peroxide concentration. By default, it measures vH2O2 concentrations from zero to 2000 ppm. The other channel measures relative saturation percentage, from zero to 100%. R.S.

In addition to analog outputs, there is also a contact for the chemical purge function. This function is important for maintaining the stability and accuracy of the HPP270 series probes. If I do not have that implemented in my simple automation system, I will rely on the interval purge cycle, which happens every 24 hours.

 

I have configured the automation system so that it matches the analog output settings of this probe. The next task is to validate the signals. To demonstrate, I want to check that 1000 ppms from the probe comes to the automation system correctly and that we have  50% percent relative saturation. So let's simulate those values. I will use a USB cable and a laptop (with Insight PC software installed). Once the probe is connected and detected, it will begin a purge cycle. We are not interested in the purge right now, we want to test the analog outputs. So, in Insight PC software, we go to “configure device.”

 

[3:57] Select Analog output one. This is configured for hydrogen peroxide. Under “Output parameter” we can select a special parameter: A Test. Then we need to define the test output level. We want to test 1000 ppms, we have to put 12.000 milliamps as the Test output level. For analog output two, which we have configured as relative saturation. We will change that also to “A Test”, to put the probe into simulation mode. We then set the Test output level to 4.000 milliamps, which is equivalent to 0% relative saturation.  Then save these test settings.

 

[4:57] Now we can connect the probe back to the automated system to see the simulation values. Channel one is now outputting 12 milliamps, which is equivalent to 1000 ppms. Our automation system is reading that correctly. Channel is now outputting four milliamps, which is equivalent to 0% relative saturation. Automation systems, and analog signals in general, are not perfect; that's why we have some signal error (1001 ppms and -0.03 % RS), but it’s pretty close.

 

[5:50] It is important to bring the probes back to the measurement mode. To do that, I will reconnect the probes to my PC to remove the simulation values I put in using Insight. Once the probe is connected, the purge cycle starts automatically. Go back to “Configure settings.” The Output parameter was hydrogen peroxide from zero to 2000, that's correct. Channel two was relative saturation, from 0 to 100%. So, we save these settings so that the probe will return to outputting the values we want.

 

[6:53] Now let’s reconnect the probe to our automation system. As always when this probe is connected, it will start the purge sequence. The purge this takes roughly two minutes. We can see that the analog signals are now outputting 3.6 milliamps, which indicates that there is no live reading available. I will pause the video and come back when the purge is complete and we are ready to perform online measurements.

 

[7:38] This was a demonstration of how to use the HPP270 (HPP272 model) as a standalone probe using analog outputs. There is another option in standalone probe use: Modbus RTU digital communication. You can watch that video here…

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