Temperature Indicator Usage

[HenrikOlsson]

Hi,
You're giving up to easily.... I don't have a 16F1827 but I have a 16F1825 which also have the temp indicator module. If you can't get it going I will bread-board it and give it a go but I have my own Projects as well and I'd rather work on those at the moment :-)

One thing I see when Reading the datasheet is this:

To ensure accurate temperature measurements, the
user must wait at least 200us after the ADC input
multiplexer is connected to the temperature indicator
output before the conversion is performed. In addition,
the user must wait 200us between sequential
conversions of the temperature indicator output.

You have set an acqusition time of 20us, 10 times less than what's required. Try DEFINE ADC_SAMPLEUS 200 and see what happens.

/Henrik.

[gunayburak]

Hi,
You're giving up to easily.... I don't have a 16F1827 but I have a 16F1825 which also have the temp indicator module. If you can't get it going I will bread-board it and give it a go but I have my own Projects as well and I'd rather work on those at the moment :-)

One thing I see when Reading the datasheet is this:

You have set an acqusition time of 20us, 10 times less than what's required. Try DEFINE ADC_SAMPLEUS 200 and see what happens.

/Henrik.

Brilliant rebound Henrik ! I was really really about to give it up I'll let you know what I get after I try what you suggest ...
You're the one "again"

[gunayburak]

Hi,
You're giving up to easily.... I don't have a 16F1827 but I have a 16F1825 which also have the temp indicator module. If you can't get it going I will bread-board it and give it a go but I have my own Projects as well and I'd rather work on those at the moment :-)

One thing I see when Reading the datasheet is this:

You have set an acqusition time of 20us, 10 times less than what's required. Try DEFINE ADC_SAMPLEUS 200 and see what happens.

/Henrik.

Hello Henrik ;

Sorry for the long delay , I had health issues and I return back to my RE-DE table as quick as possible after a quick recovery ...

I've done as you suggested and now I don't have that dependent ADC result changing problem/madness at 500 us acqusition time setting and quickly tried to get the silicon die temperature of two different pic16f1827 and I got almost the same values (one of them reads 496 and the other 497 at the very beginning of the power up..) ... Right after that I started to observe the formulas on AN1333 published by Microchip , I applied the obtained values to the formulas but I get a result which is both good and bad with raw 496 under 10 bits conversion and high range mode(4) ..

According to the formulas I get -28.59 degrees ... Well , now ...
---------------------------------------------------------------

*The good thing about this reading is that it would be an almost right conversion result if it were a positive value Because when I measure the top surface temperature of the PIC with an infrared thermometer in "object measuring mode" , I get 27.12 C' ... NOT BAD when considered the die temp. must be a little more than that !!!

*The bad thing as mentioned above is that its being a negative value

By the way there is a strange thing I keep seeing during I read the application note .. The value 0.00132 is written as 0.0132 in other forms of the calculations ...

However ;
I don't know if it is a victory or a half victory or maybe a coincidence but perhaps there is an entirely different calibration formula for this PIC ...

I'm so curious about your and all others' approaches to this problem who are interested in this built in temp. sensor module ..

Regards

[HenrikOlsson]

Hi,
I'm glad you're feeling better. As I said previously I don't have any experience in using the temp sense module in these PICs, all I'm doing is reading the datasheets.

First, lets see if a raw reading 496 makes sense.
Let's, for the exercise, say that Vt for your device matches that of the device in the App note, somewhere around 0.574V at 27C.
Vtemp, ie the voltage that the ADC measures is, in high range mode, Vdd-4*Vt or for a 5V Vdd: 5-(4*0.574)=2.704.
The RAW ADC reading is 2.704/5*1023=553.'

You're getting a value of 496 so I guess that's reasonable. I don't quite understand the values shown in Figure 4, perhaps that's using 8bit conversion, I don't know.

That's basically how far I've got as of now and I'm running out of time right now. Hopefully someone else will step in.

/Henrik.