Re: Surge protection for 4-20mA sensors and data logger?

[Steve Y <steveremove@xxxxxxxxxx>]

If you want to protect the datalogger and the sensor then you will need
protection at both ends. Just using diodes will not give you sufficient
protection, you will need gas discharge tubes as well.

If you want to protect the sensor and the electronics are not earthed, a
parallel connected device will be OK but for the datalogger you will
better with a series connected device, this will give you more
protection and react quicker.

Any true industrial product will not introduce any errors into your
signal, especially  as you are using 4/20mA signals rather than voltage

Steve
www.mtlsurge.com

andrea@xxxxxxxxxxxxxxxx wrote:
> Hi all!
>
> For my grandpa's country I am going to install tens of 4-20mA sensors,
> which will be routed through some hundreds meters of good cable to the
> data logger, at the border of the house. To give some (yes, I know it's
> impossible to give total) protection against nearby lightings, etc.. I
> thought about adding surge protection.
>
> If I understand it right, I should put one device in parallel with each
> sensor, and another device in parallel with each data logger input (i.e.
> the two ends of each cable), right?
>
> Varistors, gas-dischargers, etc.. to me it seems that a Transil diode may
> be a very cheap solution but a very effective one nonetheless. Am I wrong?
>
> And, being there two in parallel for each cable (one at the sensor and
> the other at the data logger input), are they going to false the results
> by much? I am aiming at 16bit resolution, with a full scale precision of
> about 0.1%
>
> Thank you!
> Andrea
>
>