Hello Everyone,
We have another great success to share with our readers and well wishers.
Digital Voltmeter using IC7107 was posted quite recently and we had made beautiful double sided PCB for the DVM's. Well we have managed to use the same PCB to display the Current too.
The formula is quite simple and it is not a new discovery as such. Refer to the diagram below:
We know that to measure voltage we connect the voltmeter in parallel and to measure current in a circuit we connect it in series. Now we all are aware of the famous Ohm's Law:
V = I * R
If we select the Shunt value or the R value to be 1, then the formula above reduces to:
V = I
So, keeping the points above in mind, I can effectively say that if R = 1 ohm or in orders of 1 milliohm, then when I measure the voltage it is as good as getting the current reading as V = I.
Hence the selection of the shunt value is quite crucial and the there is a a small change in the circuit. Refer the circuit below: Click Here
How did we test our Digital Ammeter?
We have selected a shunt of the specification 200A, 200 mV. So, that gets us R = 1 Milli-ohm.
Hence, by measuring the voltage across the shunt will be equivalent to calculating the current. That is, measuring 1 mV is like measuring 1A and 200mV is like measuring 200A.
Please note that the only difference in the PCB would to replace the 1Mohm used in the DVM by a 10K and the 1K resistance is removed.
In summary, we are just measuring the voltage and displaying it as current. Old school trick.
We have another great success to share with our readers and well wishers.
Digital Voltmeter using IC7107 was posted quite recently and we had made beautiful double sided PCB for the DVM's. Well we have managed to use the same PCB to display the Current too.
The formula is quite simple and it is not a new discovery as such. Refer to the diagram below:
We know that to measure voltage we connect the voltmeter in parallel and to measure current in a circuit we connect it in series. Now we all are aware of the famous Ohm's Law:
V = I * R
If we select the Shunt value or the R value to be 1, then the formula above reduces to:
V = I
So, keeping the points above in mind, I can effectively say that if R = 1 ohm or in orders of 1 milliohm, then when I measure the voltage it is as good as getting the current reading as V = I.
Hence the selection of the shunt value is quite crucial and the there is a a small change in the circuit. Refer the circuit below: Click Here
How did we test our Digital Ammeter?
We have selected a shunt of the specification 200A, 200 mV. So, that gets us R = 1 Milli-ohm.
Hence, by measuring the voltage across the shunt will be equivalent to calculating the current. That is, measuring 1 mV is like measuring 1A and 200mV is like measuring 200A.
Please note that the only difference in the PCB would to replace the 1Mohm used in the DVM by a 10K and the 1K resistance is removed.
In summary, we are just measuring the voltage and displaying it as current. Old school trick.
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