Nevzorov Problems and Solutions

During the December 1, 2015 flight, the monitor on the Liquid Water Content (LWC) side of the Nevzorov Probe failed. The sensor head (SN369) was replaced with SN 370 sensor head. After approximately 10 hours of flying, on the December 5, 2015 flight, SN370 sensor head failed. Connectivity checks are preformed on the failed heads (SN369 and SN370) and compared to a new working sensor head (SN371). Below is a handy diagram made when testing the connectivity of the Nevzorov sensor heads 369, 370, & 371. SN371 was brand new and all connections were sound. The transparent colors refer to SN369 and the opaque colors refer to SN370. Green means connectivity confirmed; magenta and red mean no connectivity was achieved during the test. Also, shown is an image of failed sensor head SN 369 showing no damage, likewise SN 370 had no damage.

The continuity test indicated that on SN369 and SN370 sensor heads, pins 2 and 13 are not connected (monitor LWC), ground pin 14 is connected to nothing, and pin 21 is connected to everything but pins 13 and 14. On the new sensor head everything works (is connected) of course. Emailed this information to skyphystech@bell.net to see if there is anything we can test or check before installing new sensor head.

During the CAPE2015 project on August 6, 2015 lightning hit the aircraft and caused the Nevzorov hot wire probe total water content(TWC) voltages (Collector and Reference) to drop to close to 0v, meaning that we were not collecting data (determined from looking at the M300). The liquid water content (LWC) was still working. When the instrument was turned off and on again, the red alarm light on the TWC side was on. The instrument was then turned off for the duration of the flight.

Due to the lightning strike and the alarm light on, the conclusion was that the Nevzorov overheated. The following steps were taken to fix the problem:

• Checked the continuity between the pins of each element [reference the image on page : shown below]
• Checked the resistance between each element [Nevzorov manual page 11]
• The elements must be within the resistance tolerances.

After checking the elements, the sensor head was reinstalled. The setting for the reference TWC was left as is and the collector voltage was changed to the setting for 20 degrees above [example: reference set at 70C and collector set at 90C].

• Turned on the power to make sure the alarm light is not on and had someone spray water on the probe. There was an indication of peaks on the M300 as well as on the collector of the TWC.
• Once there was an indication that the instrument is working, we reset both the collection and reference to the same temperature setting [70C for ground test and 110C for flight].
• Water was sprayed again to make sure that the instrument is still reading and showing peaks, which we saw on the ground test.

There was a ground test conduced August 7th (procedure mentioned above). On August 8th there was a flight conducted and the Nevzorov was closely observed. The TWC collector voltage ranged between 0.0002v and 0.8v throughout the flight In addition, there were three flights on August 11. Three of the four TWC voltages were back to normal, except the collector TWC. The initial value from each of the flights are included in the table below.

A test of the resistance, as shown in the image below, was done on August 7th and again August 17th. The values are in the table below:

The Heater resistance was 31.6 Ω.

The pilot's Com #2 is interfering with the Nevzorov measurements.