Products > Test Equipment
Brymen, difference in reading between mA and uA scale
wasedadoc:
The effect of the shunt is the current equivalent of the Ohms/Volt loading effect that one needed to be mindful of when using an analogue multimeter to measure voltage. Depending on the resistance of the voltage source the current through the meter (needed to move the needle) causes a voltage drop. Now that DMMs routinely have 10 MegOhm input resitance the efect is less of an issue but it is still something to be aware of.
BeBuLamar:
--- Quote from: wasedadoc on August 17, 2023, 02:49:34 pm ---The effect of the shunt is the current equivalent of the Ohms/Volt loading effect that one needed to be mindful of when using an analogue multimeter to measure voltage. Depending on the resistance of the voltage source the current through the meter (needed to move the needle) causes a voltage drop. Now that DMMs routinely have 10 MegOhm input resitance the efect is less of an issue but it is still something to be aware of.
--- End quote ---
The 10 Megaohm input resistance is irrelevance in the case of measuring current. It's the shunt resistor that matters.
wasedadoc:
--- Quote from: BeBuLamar on August 17, 2023, 03:19:57 pm ---
--- Quote from: wasedadoc on August 17, 2023, 02:49:34 pm ---The effect of the shunt is the current equivalent of the Ohms/Volt loading effect that one needed to be mindful of when using an analogue multimeter to measure voltage. Depending on the resistance of the voltage source the current through the meter (needed to move the needle) causes a voltage drop. Now that DMMs routinely have 10 MegOhm input resitance the efect is less of an issue but it is still something to be aware of.
--- End quote ---
The 10 Megaohm input resistance is irrelevance in the case of measuring current. It's the shunt resistor that matters.
--- End quote ---
@BeBuLamar. Try reading what I wrote more carefully.
MarioBros69:
--- Quote from: wasedadoc on August 17, 2023, 04:37:56 pm ---
--- Quote from: BeBuLamar on August 17, 2023, 03:19:57 pm ---
--- Quote from: wasedadoc on August 17, 2023, 02:49:34 pm ---The effect of the shunt is the current equivalent of the Ohms/Volt loading effect that one needed to be mindful of when using an analogue multimeter to measure voltage. Depending on the resistance of the voltage source the current through the meter (needed to move the needle) causes a voltage drop. Now that DMMs routinely have 10 MegOhm input resitance the efect is less of an issue but it is still something to be aware of.
--- End quote ---
The 10 Megaohm input resistance is irrelevance in the case of measuring current. It's the shunt resistor that matters.
--- End quote ---
@BeBuLamar. Try reading what I wrote more carefully.
--- End quote ---
In the video that appears a few comments above, what does the calibration device do to compensate for the internal resistance of the Brymen?
When the Brymen is connected to the device, its internal resistance is also being put in series with the calibration device.
IanB:
--- Quote from: MarioBros69 on August 17, 2023, 05:57:47 pm ---In the video that appears a few comments above, what does the calibration device do to compensate for the internal resistance of the Brymen?
When the Brymen is connected to the device, its internal resistance is also being put in series with the calibration device.
--- End quote ---
The calibration device produces a known fixed current using a regulator.
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