# Energy & Power Meters History by O3L09H

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```									Energy & Power Meters
History &
Measurement Principle

Ben Kemink
History and Types of Energy & Power Meters

1960’s      70’s           80’s        90’s

Current Transformer Input
Electro-dynamic                  (50 - 60 Hz)
Wattmeter
Torque Balanced                APR2
Type
Time Division Multiplier                 2885 (50 - 400 Hz)
Type                                            2533 (DC, 10Hz - 20kHz)
Digital Display Power Meters

Current Shunt Input                                                2532(DC,20Hz-400kHz))
Power Meters
WT3000 (DC, 0.1Hz-1MHz)

New Generation            Single Shot Power Meter                                 PZ4000 DC – 2MHz
QUALITY
INNOVATION
FORESIGHT
2
Thermocouple WATT-meter

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

A moving coil instrument is used to indicate the result.

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

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

QUALITY
INNOVATION
FORESIGHT
3
Electro-Dynamic WATT-meter

If fixed coils are representing the load-current and the
moving coil the voltage-representative current, we are
directly measuring electric power.

This instrument can measure DC and AC.

Frequency bandwidth Current: up to approx. 1000 Hz
Voltage: up to approx. 150 Hz

QUALITY
INNOVATION
FORESIGHT
4
Electro-Dynamic WATT-meter

QUALITY
INNOVATION
FORESIGHT
5
Thermal Watt Meter versus Electro-dynamic Meter

i

i

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INNOVATION
FORESIGHT
6

Voltage       u(t)                         Analogue          Low pass
input circuit                              multiplier        filter

X
Current             i(t)
p(t)=u(t).i(t)
T
1
input circuit                                                   Paverage   p(t).dt
T0

RMS circuit                                  To A/D
converter

MEAN circuit

RMS circuit

T
1
Average power           u (t ).i(t ).dt
T0
QUALITY
INNOVATION
FORESIGHT
7
Yokogawa 2533E

QUALITY
INNOVATION
FORESIGHT
8
Time-division multiplication principle

QUALITY
INNOVATION
FORESIGHT
9
Today: WT-Family en PZ

Sampled
Instantaneous
voltage value
Voltage                                     U(n)
u(t)
input                          A/D
circuit
Sampled
Instantaneous    DSP         To next
current                      stage
I(n)
Current           i(t)
input                         A/D
circuit

Digital
Signal
1 N
Active Power   U( n ) .I( n )                   Processing
N n 1

QUALITY
INNOVATION
FORESIGHT
10
Digital Calculations and Display: WT-Family and PZ

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INNOVATION
FORESIGHT
11
Example of true digital type
Yokogawa 2531A

QUALITY
INNOVATION
FORESIGHT
12
DSP versus CPU

   Urms
Measurement via DSP operation                      Irms
   W
 32-bit floating point operation                  VA
 80ns for WT2000                                  Var
(250ms display update)                          PF
 50ns for WT1000                                  
(100ms display update)

 Range conversion
Measurement via CPU                              
computation                                      Scaling

QUALITY
INNOVATION
FORESIGHT
13
Energy & Power Measurement Trend

1950s                            1980s                Present time               Near future

Requirement           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

V        A-D
Fixed    V                            V          A-D                           DSP
coils                         LPF                             A        A-D
Moving
A                            A          A-D
coil
A-D
DSP
A-D
Fixed
coil          A-D                         DSP         CPU
Pointer                                               CPU
of meter             Moving                                                                    CPU       CRT
coil
Fixed
MEMORY
coil                                                               MEMORY

Principle or           Electrodynamometer           Feedback time division              DSP                         DSP
multiplier system
Acquisition                                                                      Digital multiplier           Sampling A/D C
Feedback pulse width
method                                                                         Sampling A/D C
modulation
/D
Counting A C          Real time FFT analysis

Theme                       Accuracy                       Response           Isolation / Software         Probing/ Calibration

QUALITY
INNOVATION
FORESIGHT
14

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