5504GI & Temperature sensors

I am trying to read a temperature from a Betatherm sensor I've picked up from Farnell, using a 5504GI. Using resistance, there is a negative, non-linear relationship between resistance & temperature (ie. restistance drops when temperature increases, and it's not a 1:1 drop). I've tried entering a negative multiplier in Toolkit, however Toolkit crashes. (the new 1.5.2 UI looks much better by the way, but still crashes for negative multipliers).

Now, given measuring temperature via the GI unit has been done before, I figure I'm missing something.

Is there a trick used to configure Toolkit to measure the temperature, or perhaps a sensor (which can be mounted neatly internally/externally) which integrates well with Toolkit?

 

Hi mallsop,

Thanks for the info, I have logged this defect. #9576.

 

Hello again, mallsop,

Just trying to understand what you're attempting to accomplish with negative multipliers.

The threshold levels are basically numbers in the [0, 255] range, which you can alter using the multiplier and offset variables. i.e. Setting the multiplier to 3.921569 will give you a possible range of thresholds in the [0, 1000] range. If you're attempting to enter in a negative value, like -3.921569, you would end up with a range of [0, -1000] ... note that the maximum value is now the minimum value in the range, and vice versa. Unless I'm missing something, (this is possible ), couldn't you achieve the same thing by setting the multiplier to +3.921569 and setting the offset to -1000, to give you a range of [-1000, 0] to play with?

Or, if this is not what you're after, is what you're after, having the sliders arranged in a decreasing manner, (such that event 8 would be triggered before event 7, etc. when the resistance increases)?

Look forward to hearing from you!

Thanks.

 

Negative Offset

I don't need a negative multiplier, but had been asking for a negative offset. In my excitement over the new interface, I completely missed the fact that I can have one now!!

No more mentally subtracting 50 from the temperature reading to get a true value.

Thanks again guys.

 

Negative multiplier

Hi Beem,

To give a simple example (I'm making up the numbers to keep it simple), say a temperature sensor returns 0 deg = 1000 ohms, 10 deg = 900 ohms, 20 deg = 800 ohms... to turn this into a temperature, I need to multiple this by -0.1, and add an offset of 100. Using sliders in reverse order would work- however I'm also trying to broadcast the temperature.

I've started looking at different sensors, using some of the vendors from previous posts, such as Titan (www.Titanproducts.com). However the request may still be valid- at least so Toolkit dosn't crash, if not also supporting negative offsets and multipliers...

Nick- how did you go with Titan sensors- which did you end up using and did they work with the 5504GI ok?

+Mark

 

I went for temperature, humidity and light. Followingadvice here, I chose the 4-20mA option. I got a 24v supply from Farnell. All works fine.

 

I'm presuming this animal is similar to other, "standard" thermisters I've used. The rate of change itself changes with temperature. A 3rd-order polynomial is required to get "reasonably close" answers over a 0-50 degree range. "simple" constants like a multiplier and offset may give you "close enough" answers over a small temperature range but not really good enough for any practical purpose.