WM-918 Temp Sensor

Fujita Phil · Unread post by **Fujita Phil** » Wed 10/01/2007 23:43

Buggar... it finally looks like it's gonna die.

After 7 years "the rock" is tumbling. Over the last few days the temp/humd sensor has been playing up with erratic spikes in the temperature. As mentioned here and on many other sites this is usually the first part that goes on this unit and of course being discontinued doesn't really help finding a replacement.

So.... anyone have one? Know of a fix?

I maybe selling some parts off soon if not.

Any help would be much appreciated guys

Cheers
Phil

tgsnoopy · Unread post by **tgsnoopy** » Thu 11/01/2007 07:06

As a technician, it may be possible to repair if it's build from standard parts and we can identify them. However there is a good chance it's made using a component we can't source easily or at all. It quite likely uses a thermistor, getting the correct value would be very difficult without a known good one to do comparisns with.

Doe's googling the problem show anyone who has successfully repaired one?

Fujita Phil · Unread post by **Fujita Phil** » Sun 14/01/2007 21:47

Wooo... Got one!!!

Found a guy here in sunny old Dunedin that had upgraded to a Wireless station and still had the WM-918 for a spare.

The anemometer and rain gauge haven't been used yet and the temp sensor has been used for just under a year.

I swapped the sensor over tonight, after placing the new sensor inside the Stevenson Screen to adjust for a couple of hours, and recorded an identical temperature reading, a 1Â°C drop in dewpoint and a 3% drop in humidity. So that looks good enough that it doesn't affect my recorded data.

Only one problem though... I don't get to buy a new toy

ricky · Unread post by **ricky** » Mon 15/01/2007 08:05

I'd be interested in doing some reverse engineering of your faulty sensor to see how easily repairable or not they may be, failure modes and what substitutes may be possible...

I'd be happy to share the information gained If you want to send me your old one

Fujita Phil · Unread post by **Fujita Phil** » Mon 15/01/2007 16:13

Cheers Ricky

I'll "PM" you about some of the details tonight

Fujita Phil · Unread post by **Fujita Phil** » Tue 16/01/2007 09:47

Actually I'll just ask here Ricky.

Thanks for the offer on the sensor but in the meantime I may have found a new cause.

The new sensor was working absolutely fine for 24hrs and then the data spikes started happening again. I also thought that I might be getting interference from something new in the neighbourhood eg a RF signal. I then realised that I had moved some Xmas rope lights closer to the station and power source on the day that the spikes started occuring

.

Stupid me I thought. I removed them last night and about two hours later the spikes in the temperature reappeared???? Nuts

I have done a bit more research on the FreeWX forums and it sounds like a problem other people have encountered. So my next line of thought is to add some ferrite suppressors or rf chokes on the cables of all the sensors and station's unit. I'm a bit new to them and did a bit of research last night but I was wondering if anyone had any knowledge of them? Especially along the lines of the what strength I would need. Any ideas?

So in short my original sensor may actually be ok and I picked up a complete inexpensive station, sweet. Or... the 2nd sensor has the same problem but I doubt that.

Fujita Phil · Unread post by **Fujita Phil** » Tue 30/01/2007 21:55

Oh well if anyone is interested my sensor problem is now fixed.

I made contact with Gary and he suggested that I replace the extension lead and the female/female connector in case I had a dodgy lead or dry joint.

Correct. Thanks Gary. Now I have a brand new WM-918 as a replacement... sweet!