4.0 KiB
DMM = Digital MultiMeter.
Arduino library for a DMM (digital multimeter) 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. Do not expect high precision or accuracy.
Related
- https://github.com/RobTillaart/ACS712 (current measurement).
Interface
#include "DMM.h"
Constructor
- DMM() constructor.
Configuration
- begin(uint8_t analogPin, float volts = 5.0, uint16_t maxADC = 1023) configuration. Note these are the specifications of the ADC used.
- 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.
ReadVolts
One must connect GND of Arduino to the GND of the device.
[A0]---- V unknown
[GND]---- GND
or with a divider => setGain(x)
[A0]----[divider]---- V unknown
[GND]----[divider]---- GND
- float readVolts(uint8_t times = 1) read voltage. Times can be set to average multiple measurements.
- float readMilliVolts(uint8_t times = 1) convenience wrapper.
- float readNoise(uint8_t times = 1) measure the noise on the wire. Assumes connected to constant voltage e.g. GND.
ReadOhm
The schema for measuring resistors is based on a simple voltage divider. See below. This schema can be extended with a selector switch that can switch between different reference resistors.
[GND] ----[ R reference ]----[A0]----[ R unknown ]----[+5V]
- void setReferenceR(uint32_t ohm = 1000) set the reference resistor. units are Ohm, default = 1K.
- uint32_t readOhm(uint8_t times = 1) read ohm. Times can be set to average multiple measurements.
- uint32_t readKiloOhm(uint8_t times = 1) read ohm. Times can be set to average multiple measurements.
Character ohm = Ω (ALT-234 or ALT-0216 might work)
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 a (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)
- CAPS (how -> RC timing)
- RC (load 5 seconds)
- disconnect
- measure drop rate / time in micros.
- DIODE (how -> 5V or 0V)
- DigitalRead(INPUT PULLUP) => HIGH or LOW
- or 0.7 volt drop from 5V
Must
- update documentation
- update examples
- add use of AREF
- external or internal 1.1 Volt
- float setOffset(float offset) adjust the voltage used.
- this is not the voltage the ADC uses internally.
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?