I have a customer that needs to digitize the output of a strain gauge. Their power source can vary from 1.6 to 3.6V and is capable of supplying no more than 200 uA. Ideally, they want to use a differential input A/D and want a SPI output. Sample rate is super low. Maybe one sample per minute. 8 bit accuracy is acceptable. The design is high volume 100-200K units and very cost sensitive The Maxim MAX1391 is being considered. As an alternative, I offered the AD7468 + AD8237. I have a few questions:
Attached is my initial idea
A couple new thoughts. Perhaps the AD8236 is a better fit for the Instrumentation amp. It is much lower power. Regarding the reference, I looked for something cheaper than the Maxim part and considered the following:
Both are very low power
Do you know if the bridge will generate both positive and negative voltages? Or are they interested in the positive swing only? In any case, it may be necessary to shift the output to account for bridge offsets and/or negative voltages. I noticed this is missing from your sketch.
Also, how much gain do they need and how large is the bridge offset? The following article may shed some light into why I'm asking
I'm pretty new in the forum I don't have much experience in fact this is my first cuestion in the forum, I was wondering if you could help me to find a sollution a similar problem that Lionelwallace has exposed time ago.
I need to digitize the output of a strain gauge. Their power source normally will be close to 3.6 but it should be possible use a step up for use with 5 v the consumption is critically I mean must be very, very low consumption this circuit need the positive swing only, and the resollution must be at least 10 bits Ideally 12, SPI output. The maximum sample rate is 15ms.
Could you please help me to find a sollution
Thanks in advance.