elowro / meter-accuracy

❓Meter Accuracy - Portable and open repository of various DMMs accuracy expressed in uncertainty based on range, reading and absolute offset.

Meter Accuracy Data Representation

Purpose

Meter Accuracy Data Representation format, abbreviated as MACDR. JSON file structure.

Portable and open repository of various meters accuracy expressed in uncertainty based on range, reading and absolute offset. Intended for machine to machine consumption.

Data

All specified meters data is located in /Meters folder, for easy M2M consumption index.js is auto-generated.

MACDRv1 Format Specification

Format Identifier

org.macdr.v1

Values:

All uncertainties values are floating-point numbers (64bit Double) and assumed to be either positive or negative so 0.1 means ±0.1.

Filename:

Every unique meter model will be represented by a separate json file. Filename should be created as follows:

{Manufacturer}_{Model Name}.json

Example:

Keysight_3458A.json

Metadata:

• manufacturer - manufacturer short name
• manufacturer_full - manufacturer name
• model_name - model full name
• uid - unique product identifier (reverse dns)
• product_identifier - manufacturer's product identifier
• source - description of source (usually datasheet)
• source_url - link to source (usually to a datasheet)
• photo_url - link to meter photo²
• photo_url_author - author¹
• usdz_model_url - link to meter USDZ 3d model¹
• usdz_model_url_author - author¹

¹-optional

Important: All assets must be public domain!

Specs

All meter specs are expressed as key-values where key is amount of hours from calibration.

Absolute Quantities

Identifier	Unit	Description
absolute.voltage.dc	Volts	DC Voltage
absolute.current.dc	Amperes	DC Current
absolute.voltage.ac	Volts	AC Voltage
absolute.current.ac	Amperes	AC Current
absolute.resistance.2w	Ohms	Resistance 2-Wire
absolute.resistance.4w	Ohms	Resistance 4-Wire
absolute.frequency	Herz	Frequency
absolute.capacitance	Farad	Capacitance at Frequency
absolute.inductance	Henres	Inductance at Frequency
absolute.impedance.phase	degrees	Phase Angle of Impedance

This list is NOT part of the MACDRv1 specification, more identifiers will be added along the way.

Transfer Quantities

Identifier	Unit	Description
transfer.voltage.dc	Volts	DC Voltage Transfer
transfer.voltage.ac	Volts	AC Voltage Transfer
transfer.voltage.acdc	Volts	AC/DC Voltage Transfer
transfer.resistance.2w	Ohms	Resistance 2-Wire Transfer
transfer.resistance.4w	Ohms	Resistance 4-Wire Transfer

This list is NOT part of the MACDRv1 specification, more identifiers will be added along the way.

Structure

Main

{
    "format": "{string}",
	"uid": "{string}",
	"manufacturer": "{string}",
	"model_name": "{string}",
	"product_identifier": "{string}",
	"source": "{url}",
	"source_url": "{url}",
	"transfer": {
		"{Measurement Identifier}": [ ]
	},
	"absolute": {
		"{Measurement Identifier}": [ ]
	}
}

Specs

• reading - fraction of reading
• range - fraction of used range
• absolute - absolute offset (in relevant unit)

Absolute

• hours_from_calibration - hours limit from meter calibration/adjustment
• confidence - (optional) some manufacturers specify confidence (0.99 means 99%)
• aperture_seconds - (optional) some manufacturers specify minimal aperture
• nplc - (optional) some manufacturers specify minimal bumber of power line cycles

{
	"hours_from_calibration": 0,
	"seconds_between_measurements": 0,
	"absolute": 0.0,
	"reading": 0.0,
	"range": 0.0
}	

Transfer

• seconds_between_measurements - used in transfer specs, max time between measurements
• required_temperature_celsius - (optional) some manufacturers specify transfer temperature
• maximum_temperature_change - (optional) maximum temperature change between measurements or from Tref/Tcal
• confidence - (optional) some manufacturers specify confidence (0.99 means 99%)
• aperture_seconds - (optional) some manufacturers specify minimal aperture
• nplc - (optional) some manufacturers specify minimal bumber of power line cycles

{
	"seconds_between_measurements": 0,
	"required_temperature_celsius": 0,
	"maximum_temperature_change_celsius": 0,
	"absolute": 0.0,
	"reading": 0.0,
	"range": 0.0
}	

Absolute: DC Voltage

• range - range in Volts

{
	"absolute.voltage.dc": [
		{
			"range": 0, 
			"accuracy": []
		}
	]
}

Absolute: DC Current

• range - range in Amperes

{
	"absolute.current.dc": [
		{
			"range": 0, 
			"accuracy": []
		}
	]
}

Absolute: Resistance

• range - range in Ohms
• current - current used in Amperes

{
	"absolute.resistance.4w": [
		{
			"range": 0, 
			"current": 0,
			"specs": []
		}
	]
}

Absolute: AC Voltage

• range - range in Volts
• frequency_from - frequency range start, Herz
• frequency_to - frequency range end, Herz

{
	"voltage.ac": [
		{
			"range": 0, 
			"frequency_from": 0.0, 
			"frequency_to": 0.0, 
			"specs": []
		}
	]
}

meter-accuracy's Issues

Secondary specification parameters?

Is it planned to have secondary and additional parameters? Just to take simple DCV function for example:

• Tempco factor (with ACAL and without ACAL ;)
• High-voltage additional uncertainty due to HV divider heating
• Factory calibraiton adder
• Noise specification adder from fast modes of operation
• Null errors for lowest ranges (esp important for nanovoltmeters and small signals)
  Often resistance also have various modes with different specs (e.g. OCOMP ON or OFF).
  It's impossible to have useful calculation of instrument provided uncertainty without having complete specs dataset.