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153 lines
4.0 KiB
Markdown
153 lines
4.0 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/DMM/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/DMM/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/DMM/blob/master/LICENSE)
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[](https://github.com/RobTillaart/DMM/releases)
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# DMM = Digital MultiMeter.
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Arduino library for a DMM (digital multimeter) class.
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## Description
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DMM is a class that uses the Arduino analogRead to make measurements.
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It is based upon the UNO but will work on some other boards too.
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The first version only works as a voltmeter, DC only.
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It is meant to be extended in the future to be a complete Digital MultiMeter class.
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that includes amps ohms, diode testing etc.
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This is an old 'toy' project, wrapped into a class.
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Do not expect high precision or accuracy.
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#### Related
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- https://github.com/RobTillaart/ACS712 (current measurement).
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## Interface
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```cpp
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#include "DMM.h"
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```
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#### Constructor
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- **DMM()** constructor.
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#### Configuration
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- **begin(uint8_t analogPin, float volts = 5.0, uint16_t maxADC = 1023)** configuration.
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Note these are the specifications of the ADC used.
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- **void setMaxVoltage(float maxVoltage)**
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- **float getMaxVoltage()**
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- **void setGain(float factor = 1.0)** GAIN e.g. due to voltage divider.
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A 25V to 5V divider has a factor = 5.
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- **float getGain()** returns the set gain.
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#### ReadVolts
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One must connect GND of Arduino to the GND of the device.
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```
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[A0]---- V unknown
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[GND]---- GND
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or with a divider => setGain(x)
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[A0]----[divider]---- V unknown
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[GND]----[divider]---- GND
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```
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- **float readVolts(uint8_t times = 1)** read voltage.
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Times can be set to average multiple measurements.
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- **float readMilliVolts(uint8_t times = 1)** convenience wrapper.
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- **float readNoise(uint8_t times = 1)** measure the noise on the wire.
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Assumes connected to constant voltage e.g. GND.
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#### ReadOhm
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The schema for measuring resistors is based on a simple voltage divider.
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See below. This schema can be extended with a selector switch that can
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switch between different reference resistors.
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```
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[GND] ----[ R reference ]----[A0]----[ R unknown ]----[+5V]
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```
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- **void setReferenceR(uint32_t ohm = 1000)** set the reference resistor.
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units are Ohm, default = 1K.
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- **uint32_t readOhm(uint8_t times = 1)** read ohm.
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Times can be set to average multiple measurements.
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- **uint32_t readKiloOhm(uint8_t times = 1)** read ohm.
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Times can be set to average multiple measurements.
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Character ohm = Ω (ALT-234 or ALT-0216 might work)
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#### Calibration
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- **float readNoise(uint8_t times = 1)** get noise level for accuracy.
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## Operation
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Basic operation is to connect the Arduino GND to the projects GND (or - )
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and use the configured analog pin to measure a (positive) voltage.
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By adding a voltage divider one can measure larger voltages.
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The divider factor can be set with **setGain(factor)**.
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To elaborate.
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- GND, VCC
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## Future
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#### Functional
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- AMPS (how -> measure voltage over a known resistor)
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- CAPS (how -> RC timing)
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- RC (load 5 seconds)
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- disconnect
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- measure drop rate / time in micros.
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- DIODE (how -> 5V or 0V)
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- DigitalRead(INPUT PULLUP) => HIGH or LOW
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- or 0.7 volt drop from 5V
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#### Must
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- update documentation
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- update examples
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- add use of AREF
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- external or internal 1.1 Volt
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- **float setOffset(float offset)** adjust the voltage used.
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- this is not the voltage the ADC uses internally.
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#### Should
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- investigate noise
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- analogReference(EXTERNAL) for external voltage for build in ADC
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- support external ADC e.g. ADS1115 for 16 bit resolution.
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#### Could
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- multichannel compare
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- schema for
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- scope functionality?
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#### Won't
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