Hi all,
I have a TC7106 based 100A ammeter (with an FSD of 100mV). It all works reasonably well but shows a permanent offset of about -7A.
The actual circuit appears to be much the same as the one on the datasheet.
The circuit is powered by a 7805 regulator connected to a +12V supply. The reading is still there when Vin+ and Vin- are shorted together.
When powered by an isolated battery the problem disappears.
I understand the cause is an offset between the negative on the shunt that connects to Vin- and the negative of the supply to the 7805 regulator.
Theoretically all the negatives should be at the same potential, but the circuit is being used in a boat and quite often [in marine electricals] the different negatives can be a few mV apart and it is extremely difficult to correct this issue.
In the circuit GND, ANALOGUE COMMON, Refin- and Vin- are all connected together and in turn connected to the negative of the regulator.
The "negative" of the shunt sits about 6mv above the negative of the regulator which is introducing the offset.
The ideal solution is to have the input floating with respect to GND so that the offset doesn't interfere with the reading.
Is it just a matter of disconnecting the GND from ANA. COMMON and all the negative inputs on the 7106?
I have a TC7106 based 100A ammeter (with an FSD of 100mV). It all works reasonably well but shows a permanent offset of about -7A.
The actual circuit appears to be much the same as the one on the datasheet.
The circuit is powered by a 7805 regulator connected to a +12V supply. The reading is still there when Vin+ and Vin- are shorted together.
When powered by an isolated battery the problem disappears.
I understand the cause is an offset between the negative on the shunt that connects to Vin- and the negative of the supply to the 7805 regulator.
Theoretically all the negatives should be at the same potential, but the circuit is being used in a boat and quite often [in marine electricals] the different negatives can be a few mV apart and it is extremely difficult to correct this issue.
In the circuit GND, ANALOGUE COMMON, Refin- and Vin- are all connected together and in turn connected to the negative of the regulator.
The "negative" of the shunt sits about 6mv above the negative of the regulator which is introducing the offset.
The ideal solution is to have the input floating with respect to GND so that the offset doesn't interfere with the reading.
Is it just a matter of disconnecting the GND from ANA. COMMON and all the negative inputs on the 7106?