Energy & Power Meters History & Measurement Principle

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Energy & Power Meters History &

Measurement Principle

Ben Kemink

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2 ^FORESIGHT

INNOVATION QUALITY

History and Types of Energy & Power Meters

1960’s 70’s 80’s 90’s

Current Transformer Input

Torque Balanced

Type APR2

Time Division Multiplier Type

2885 (50 - 400 Hz)

Digital Display Power Meters

2533 (DC, 10Hz - 20kHz)

Electro-dynamic

Wattmeter (50 - 60 Hz)

Traditional Stable Loads

Current Shunt Input 2532(DC,20Hz-400kHz))

WT1600 (DC,0.5Hz-1MHz)) WT230 (DC,0.5Hz-100kHz))

Digital Sampling Power Meters

WT3000 (DC, 0.1Hz-1MHz) Traditional

Stable Loads

Single Shot Power Meter

New Generation Un-Stable Loads

PZ4000 DC – 2MHz

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The heating-wire is very thin and easily burned out by an over-current.

This instrument can be used to measure both DC and AC.

Frequency bandwidth Current: up to approx. 10 MHz Voltage: up to approx. 100 kHz A moving coil instrument is used to indicate the result.

The thermocouple generates a DC-voltage proportionally to the temperature difference of the junction and the

reference point.

Thermocouple WATT-meter

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4 ^FORESIGHT

This instrument can measure DC and AC.

Frequency bandwidth Current: up to approx. 1000 Hz Voltage: up to approx. 150 Hz If fixed coils are representing the load-current and the moving coil the voltage-representative current, we are directly measuring electric power.

Electro-Dynamic WATT-meter

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Electro-Dynamic WATT-meter

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6 ^FORESIGHT

Thermal Watt Meter versus Electro-dynamic Meter

i

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



T

0

).

( ).

T (

1 u t i t dt

Average power

To A/D converter Voltage

input circuit

Current input circuit

RMS circuit

MEAN circuit

RMS circuit

u(t)

i(t) p(t)=u(t).i(t)

Low pass filter

Analogue multiplier

X



 ^T T 0 average 1

P p(t).dt

Analogue Measurement, Digital Readout

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8 ^FORESIGHT

Analogue calculation, Digital Readout Yokogawa 2533E

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Time-division multiplication principle

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1 0

FORESIGHT INNOVATION

QUALITY

i(t) u(t)

Sampled

Instantaneous current

I(n) Sampled

Instantaneous voltage value U(n)

DSP

Voltage input circuit

A/D

To next stage Current

input circuit

Digital Signal Processing

I. U

⁽ⁿ⁾

N 1

n (n)

N Power 1

Active





A/D

Today: WT-Family en PZ

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Digital Calculations and Display: WT-Family and PZ

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1 2

QUALITY

Example of true digital

Yokogawa 2531A

type

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Measurement via DSP operation

 32-bit floating point operation

 80ns for WT2000

(250ms display update)

 50ns for WT1000

(100ms display update)

 Urms

 Irms

 W

 VA

 Var

 PF

 

Measurement via CPU computation

 Range conversion

 

 Scaling

DSP versus CPU

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1 4

QUALITY

Energy & Power Measurement Trend

Requirement

1950s 1980s Present time Near future

Stability / Repeatability Accuracy / Bandwidth Real time / Analysis Efficiency / Control Background Boom of house appliances Boom of Inverter Harmonics / Flicker Ecology / Energy Object / Target Commercial frequency Static power Static power / Analysis Transient power

Sensing Coil CT, DC/CT Non inductive shunt High freq . probe/sensor

Method Moving coil Analog circuit or IC Digital circuit or IC Digital IC

Principle or Acquisition

method

Electrodynamometer Feedback time division multiplier system Feedback pulse width

modulation Counting A/D C

DSP Digital multiplier

Sampling A/D C Real time FFT analysis

MEMORY

DSP Sampling A/D C

Theme Accuracy Response Isolation / Software Probing/ Calibration

Fixed coils Moving coil

Fixed coil Moving coil Fixed

coil Pointer

of meter

V A

A-D

LPF

CPU

V A

A-D A-D

DSP CPU MEMORY

V A

A-D A-D A-D A-D

DSP

CPU CRT