EAF External Temperature Sensor Problem

w8xn

My new EAF (5V USB version) reports a reasonable 31C value for the internal temperature sensor, but when I connect the included ZWO-EAF-Sensor external temperature sensor, the value reported in the ZWO EAF Setup box (V6.0.5 FW:3.1.7) is 78.4C. Likewise, the value reported in the ASCOM Device hub is 78.4C and 173.1F when Fahrenheit is selected. It looks like there is some kind of double temperature conversion going on. Is there a setting for this? Even if 78.4 is the measured temperature in degrees F, the calibration of the external sensor isn't all that great as the temperature I measure with my Fluke 54 II B temperature probe (tied to the external sensor) is 66.9F or 19.4C. (Yes, I know that it is delta T that is of interest.) Perhaps this question has been previously addressed in the forum.

Bruce

w8xn

Upgrading the EAF firmware from 3.1.9 to 3.2.3 fixed the problem. The EAF external temperature probe now reads within 0.2C of the Fluke probe at room ambient.

Bruce

jwillemse

Hi Bruce, I have the a similar issue with my EAF, but with EAF firmware version 3.3.5 which seems to be the latest release. Connecting the external temperature sensor at ambient ₂₀ celsius shows a seemingly random temperature. Did the issue ever return with your EAF?

Steps to reproduce issue with my EAF:
-Connect EAF without external temp sensor connected: ASCOM shows T: 20.5C.
-Connect external temp sensor: ASCOM shows T:83.8C.
-Disconnect external temp sensor: ASCOM shows T:20.5C.
-Connect external temp sensor: ASCOM shows T: 56.2C.

Temp sensor is attached to the tube with insulating self-adhesive foam.
I tried re-flashing the 3.3.5 firmware, but the issue persists.

Thanks.

w7ay

jwillemse -Connect external temp sensor: ASCOM shows T:83.8C.

Check if you have a defective sensor.

Measure the resistance of the probe (between tip and ring of the 3.5mm plug). At 25ºC, it should read 100KΩ. For other temperatures, see this chart, it should be pretty close:

http://www.learningaboutelectronics.com/Articles/Thermistor-output-table.php

The firmware bug (that was fixed in 3.3.3 and 3.3.5) causes the types of errors that I had measured in post #3 of this thread (a sudden dip in temperature readout right in the neighborhood of 0ºC):

https://bbs.astronomy-imaging-camera.com/d/14628-eaf-randomly-changes-temperature-to-16-degs

Chen

w8xn

I, too, suspect that you have a bad external temperature sensor as the readings when your external sensor is connected are incorrect and not repeatable. I am quite sure that the problem that I reported in my original post was an error in the EAF firmware that was fixed in v3.2.3, which is the version that I have been using until today. Out of curiosity, I flashed the 3.3.5 firmware to my EAF, and it seems to work fine reporting the correct external temperature both in ASCOM Device Hub and SharpCap. I run the EAF with Windows 10 on a PLL EAGLE4S. I would be interested to hear what you find out about your sensor if you are able to "ohm it out". I get 119.5 kohms at 20.5C between the sleeve and tip with my Fluke DMM. Not sure what is on the ring.

Bruce

w7ay

w8xn I get 119.5 kohms at 20.5C between the sleeve and tip

You are right, between sleeve and tip; my mistake. The ring (with sleeve as ground return) is used for the "hand controller" data.

Chen

jwillemse

Thank you for your replies.

I checked things and my sensor appears to be ok, measured around 120kohms at room temperature with the Fluke.

I tested my EAF unit in the climate chamber at work and the internal sensor is also showing incorrect temperatures. At 0 celsius it shows around 19 celsius in ASCOM, and at 40 celsius it shows around 26.5 celsius in ASCOM. Perhaps the ADC or ref voltage in the unit is defective, I`ll return it for inspection, keep you posted!