In the data sheet of LA-55P, the minimum measuring resistance is 50 ohm if 15V dc supply is used. The nominal measuring current in primary is 50 A. If the sensor is used for a range of 0-20 A (RMS) , can I use a measuring resistance less than 50 ohm (say 10 ohm)?
Similarly in voltage sensors also, if we use LV-25P for a measuring voltage range of 200 V, can I use a measuring resistance less than 100 ohm (say 50 ohm)?
What are the deciding factors of minimum measuring resistance ?
Hi Jayasankar, it may work but it is usually not wise to go against the recommendations of the data sheet. There is not much information on the internals of this particular device, but the resistor is likely to help internally limit the current. Potentially, using a smaller resistance, the sensor could try and over power itself and burn out (but this would give you a smaller voltage output anyway). It seems using a larger resistance, up to 100 Ohm is OK and this would give you a larger output voltage range. If you really have to measure the output across a 10 Ohm resistor (not sure why) I would use it in series with a 40 Ohm so you keep to the specifications.
Agreed you should not be using the sensor out of spec. In this case, one or both of two potential issues could arise if you use lower measuring resistance: (1) at the upper limit of the dynamic range, your circuit may be overloaded above the current limit (if you do not have current-limiting circuit in your design) and risks damage to the sensor or the power supply - given that it appears a supply voltage (bias) is required, (2) the sensor is operating outside of the linear region (resulting in out of spec linearity error).
@Phil and Kin Thank you for the reply. keeping two resistors in series seems to be okey for my application.
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