Electronics > Projects, Designs, and Technical Stuff
Looking for ideas to DIY uA Meter (shunt amplifier)
<< < (3/6) > >>
Gyro:
Yes, that's a TIA circuit as previously advised.

The output of the opamp swings until the current through the feedback resistor balances the current coming from the source (at the inverting input).

Google Transimpedance amplifier.
Kleinstein:
The circuit from that last link is the TIA circuit.  The current is flowing through the resistor in the feedback path of the OP.  So there is no voltage amplification, but the OP works as a buffer and suppresses the burden voltage, so that one can use a larger resistor. The input terminals are the far left of the 1 st. circuit part. However this only the very basic circuit, without protection and it may oscillate with a capacitive source. So the pA meter thread is probably the better starting point - there should be protection parts included.
If just the µA range and no need to worry about pA's the choice of OP is relaxed quite a bit.

The shunt + amplifier circuit is good for high currents like 1 mA and up. Though it still works for lower currents, down to maybe 10 pA resolution.
The TIA circuit can work down to very low currents, but is limited at higher current like more than 1-10 mA, as the amplifier must provide the current and due to self heating at that higher current.

While the shunt circuit kind of needs a low offset (e.g. AZ type) amplifier, the TIA type circuit can get away with a more normal OP, as the offset is relative to the output voltage range, so something like 10 or 100 times less important.
001:

--- Quote from: Kleinstein on December 14, 2018, 10:08:33 am ---The circuit from that last link is the TIA circuit.  The current is flowing through the resistor in the feedback path of the OP.  So there is no voltage amplification, but the OP works as a buffer and suppresses the burden voltage, so that one can use a larger resistor. The input terminals are the far left of the 1 st. circuit part. However this only the very basic circuit, without protection and it may oscillate with a capacitive source. So the pA meter thread is probably the better starting point - there should be protection parts included.
If just the µA range and no need to worry about pA's the choice of OP is relaxed quite a bit.

The shunt + amplifier circuit is good for high currents like 1 mA and up. Though it still works for lower currents, down to maybe 10 pA resolution.
The TIA circuit can work down to very low currents, but is limited at higher current like more than 1-10 mA, as the amplifier must provide the current and due to self heating at that higher current.

While the shunt circuit kind of needs a low offset (e.g. AZ type) amplifier, the TIA type circuit can get away with a more normal OP, as the offset is relative to the output voltage range, so something like 10 or 100 times less important.

--- End quote ---

Thank You!

But I don`t need pA range
I`m interested of 1-100mA 0-100kHz with minimal burden voltage
Kleinstein:
For the 1 - 100 mA range, a µA meter would not help very much  |O  :-DD

How important is minimal burden ? Though difficult it might still be possible to use an TIA at 100 mA,  if minimal burden is really required.

The more normal way would however be a shunt with amplifier in this current range. For 100 kHz this would already be a relatively fast amplifier, probably in 2 stages.
001:

--- Quote from: Kleinstein on December 14, 2018, 11:01:36 am ---For the 1 - 100 mA range, a µA meter would not help very much  |O  :-DD

How important is minimal burden ? Though difficult it might still be possible to use an TIA at 100 mA,  if minimal burden is really required.

The more normal way would however be a shunt with amplifier in this current range. For 100 kHz this would already be a relatively fast amplifier, probably in 2 stages.

--- End quote ---

Sorry for misunderstood
Is it possible to keep burden voltage at shunt in regulation range of PS?
For example 5v PS that regulated 4% or 200v regulated 0.5%
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod