Maverik ET-72/73 and ET-722/733 difference & thermistor data sheet

[Davide Arzarello]

Hi

according to heatermeter wiki the standard probe is a 10K NTC thermistor and is highly commended to use ET-72/73 but also ET 732/733 are acceptable

I have sourced on Amazon some Maverik compatible thermistor with ET-732/733 (below the link ) and works fine with that thermometer but if I measure the resistance is more than 1 Mhom @ room temerature ! How can they work with 10K voltage divider mounted on hetermeter ??

https://goo.gl/DDq95W

I try also to search for the official data sheet of maverick thermistor and I found an old post with the data sheet of ET-73 and is rated 200Khom @ 25C so again how can it works with standard heatermeter voltage divider ??

very confused and not sure what temperature probe source since the spec says 10K NTC but no one of the suggested seems to have that value

anyone can clarify ??

thanks
Davide

 

[Bryan Mayland]

Where did you see that the standard probe is 10K NTC Thermistor? There's no standard probe really, it is whatever you plug into it. You may be seeing that "Recommended HeaterMeter resistance: 10k ohm (standard)". This is the other half of the voltage divider that is soldered into HeaterMeter which is independent of the probe. Changing this resistor will change the resolution of the input by adjusting the most sensitive region up or down (see ADC Resolution Tool).

Something else that is mentioned in the wiki is the "ambient" thermistor, which can be a 10K NTC and would replace a probe input so it isn't really recommended. If folks want an ambient reading, they usually just plug in a probe and leave it dangling outside the grill.

 

[Davide Arzarello]

Where did you see that the standard probe is 10K NTC Thermistor? There's no standard probe really, it is whatever you plug into it. You may be seeing that "Recommended HeaterMeter resistance: 10k ohm (standard)". This is the other half of the voltage divider that is soldered into HeaterMeter which is independent of the probe.

Thanks for the clarification, maybe I just misunderstood the sentence on the wiki "The standard HeaterMeter build uses 10000 (10k) ohm resist"

so this refers to the “standard” voltage divider soldered on the the board right ?

Changing this resistor will change the resolution of the input by adjusting the most sensitive region up or down (see ADC Resolution Tool).

I still have a doubt what is the rated value @25c of the Maverik probe
ET-72/73 according to what I found seems 200K right ?
ET-722/733 the clone I bought are around 1Mhom

what are best voltage diver resitor value for that sensors types?

Can you explain little bit how can I sues the ADC resolution tool (or provide me a link to read about) to calcualte the resistor?

thanks
Davide

 

[Davide Arzarello]

Hi

I got directly from Maverik the data sheet of the ET-73 and ET-732 thermistor probe

I don't find a way to attach the PDF , maybe are useful for other people , but I can confirm

ET-73 is rated 200K @ 25c
ET-732 is rated 1M @ 25c

can someone help me understanding the "right" resistor divider value for both options ?

Davide

 

[Bryan Mayland]

For the "right" value, you could use the suggested values on the wiki!

The ADC Resolution Tool shows you the response curve of the selected probe with your selected fixed resistance. You want the curve to have the greatest slope at your desired highest precision temperature, i.e. if you want your best precision then adjust the resistance until the slope is most-vertical at that temperature. You see that the ET-72/73 with 10k is centered at 250F and the ET-732 with 22k is centered at 250F. Mousing over the graph will show you how much one "ADC tick" is, which is the max quantization error at that point.

Note that shifting the curve with different resistors can destroy your accuracy at lower/higher temperatures, like an ET-732/22k has greater than 3F error at 50F.