HMC1052 range and consistency control?

I have installed a number of these compasses on identical boards, and I've found that not only do their measurements differ, but also even the range of values.

at the same position and direction, they give significantly different values for +/-. This is a slight annoyance having over 50 boards to go in the firmware and adjust the offsets before calculating the direction, but is this a common thing?

Lastly and more worrying is the difference in ranges that the values give when i read from them in all 360 degrees with maybe 16 increments. For example, one compass may give a maximum value for + of say 2 volts and a minimum of 1 volt, with the same for the -. Another may give a range for + of 1.5 volts to 1.7 volts, and the - may give 1 volt to 2 volts. And another will have .8 volts to 2.5 volts for + and 1.1 to 1.15 volts for -. Are these common issues? they are all implemented on identical boards.

Reply to
Johnny Chang
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Did you use the flip coils to reset the offsets? How did you measure it? They don't output volts, it is a resistor bridge. Maybe your amplifier circuit has some offset or different gain? Can you measure the resistors of different parts before soldering (and after applying a pulse to the flip coils)?

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Frank Buss, fb@frank-buss.de
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Reply to
Frank Buss

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We obviously have a considerably different idea of the meaning of 'compass'. To me, this is an item containing a magnet and pivot, that self adjusts to point (more or less) at magnetic north.

So what are you talking about?

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 [mail]: Chuck F (cbfalconer at maineline dot net) 
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Reply to
CBFalconer

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tems.de

Er whoops, instead of + and -, i meant bridge1 +/- difference and bridge2 +/- difference. We use the same amplification circuit for each one, but I can test them and measure them whenever I get back to lab. Yeah, we send a pulse to set/reset.

Reply to
Johnny Chang

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