I'm trying to use an ACS770LCB-100U-PFF-T hall effect current sensor to measure the DC current coming from a solar array.
This sensor gives a linear voltage output up to 5V according to the DC current applied to its terminals (up to 100A)
Without even wiring it into the array, the sensor gives readings of 10A (0.5V at the output).
I've also tried the ACS770LCB-100B-PFF-T (bidirectional input currents possible) and this gives readings of 40A without being connected to any input.
This is a rough diagram showing how I've wired it up. I'm using an ESP32 and an MCP3008 external adc, though I've previously wired the unidrectional sensor directly into an arduino analog input and had the same issues.
Any suggestions as to what could be causing the non zero readings?
Quiescent output voltage (VIOUT(Q)). The output of the device when the primary current is zero. For bidirectional current flow, it nominally remains at VCC⁄ 2. Thus, VCC = 5 V translates into VIOUT(QBI) = 2.5 V. For unidirectional devices, when VCC = 5 V, VIOUT(QUNI) = 0.5 V. Variation in VIOUT(Q) can be attributed to the resolution of the Allegro linear IC quiescent voltage trim, magnetic hysteresis, and thermal drift.
Ratiometric sensors like this don't usuallt go fully rail-to-rail. Its very common to see 10% to 90% of the
supply voltage being the output voltage range. This makes implementing the internal circuitry easier,
and allows for manufacturing variation to be calibrated out as 9% for 10% can be handled, but -1% for 0%
isn't possible.
