Machsupport Forum
Third party software and hardware support forums. => PoKeys => Topic started by: chrisisbd on October 31, 2012, 05:52:10 PM
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I have just bought a pokeys56e to do some monitoring jobs on our small boat.
Specifically I am going to use it to measure some battery voltages.
Does anyone know how accurate the voltage reference on the pokeys56 is? I don't need absolute accuracy as I can of course calibrate the measurement myself (and will have to use a voltage divider anyway as I'm measuring more than 3.3 volts) but I do need the voltage reference to be stable within 1% or so.
Secondly what sort of protection should I provide for the inputs, is there a standard way to do it. The boat electrical environment is fairly noisy (essentially much like a car).
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The voltage reference is present in the low-drop voltage regulator on the board, which is LD1117 (datasheet says that its temperature stability is typically around 0.5%, while it should be generally 1% accurate at 25 °C and 2% in all temperature range).
Regarding the protection - I would suggest a zener or suppressor diode between voltage divider and PoKeys, and a small choke would make it even better.
However, you should pay attention also to the power supply - suppressor and choke are mandatory here.
Generally, anything that goes in or out of PoKeys (except the network cable) must be protected by suppressor (or zener).
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OK, thanks, that's just the sort of advice/information I was after.
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I have never read anything from pokeys about suppressor diodes or zeners on every line, can you provide a little more info, part numbers, etc ?
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This information will be included in the PoKeys manual in two weeks time.
Generally, it is preferred to include protection of power and signal inputs and outputs in noisy environments.
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Here is the circuitry that can be used to protect the PoKeys inputs if the device is used in (electrically) noise environments.