[Tinyos-help] Sensirion SHTxx batch differences?

[Simon Davis]

Hello,

I've bought a number of Sensirion SHT11 and 15s as seperate chips to use
with Tmote Sky's. I'm soldering them onto ribbon cable and mounting them
within modified cable glands as weather-proof housings. I want to ensure
that my process isn't affecting the calibration of the sensors.

What I'm wondering is whether there's a possibility that Sensirion's
humidity calibration process is producing batches of sensors which agree
in calibration with each other but not with other batches. For instance I
have:

11 SHT15s (the number on them is 436 - week 43 2006) all reading 49-50%.
3 SHT11s (236) reading 58-59%.
2 SHT11s (066) reading 53-54%.

I realise there are different accuracies between models but I think the
three batches appear to have differing calibrations so that each batch is
in agreement within itself but not the other two? The temperature
readings on all are within accuracy and are evenly distributed. All have
been hand soldered, I don't think this has affected them.

Does anyone else notice anything like this?

Thanks

Simon

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