DMM = Digital MultiMeter.

Arduino library for a DMM class.

Description

DMM is a class that uses the Arduino analogRead to make measurements. It is based upon the UNO but will work on some other boards too.

The first version only works as a voltmeter, DC only. It is meant to be extended in the future to be a complete Digital MultiMeter class. that includes amps ohms, diode testing etc.

(this is an old 'toy' project, wrapped into a class)

https://github.com/RobTillaart/ACS712 (current measurement).

Interface

DMM() constructor.

Configuration

begin(uint8_t analogPin, float volts = 5.0, uint16_t maxADC = 1023) configuration.
void setMaxVoltage(float maxVoltage)
float getMaxVoltage()
void setGain(float factor = 1.0) GAIN e.g. due to voltage divider. a 25V to 5V divider has a factor = 5.
float getGain() returns the set gain.

Read

float readVolts(uint8_t times = 1) read voltage. Times can be set to average multiple measurements.
float readMilliVolts(uint8_t times = 1) convenience wrapper.

Calibration

float readNoise(uint8_t times = 1) get noise level for accuracy.

Operation

Basic operation is to connect the Arduino GND to the projects GND (or -) and use the configured analog pin to measure (positive) voltage.

By adding a voltage divider one can measure larger voltages. The divider factor can be set with setGain(factor).

To elaborate.

GND, VCC

Future

Functional

AMPS (how -> measure voltage over a known resistor)
OHM (how -> known divider)
DIODE (how -> 5V or 0V)
CAPS (how -> RC timing)

Must

update documentation
update examples
add use of AREF
- external or internal 1.1 Volt

Should

investigate noise
analogReference(EXTERNAL) for external voltage for build in ADC
support external ADC e.g. ADS1115 for 16 bit resolution.

Could

multichannel compare
schema for
scope functionality?

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