Portable, solid state wattmeter with wideband (dc to 1 MHz) linear multiplier which provides true four quadrant operation permitting instantaneous indication of real power as oscilloscope display is described

Landes, L. G.

Liu, Y. Y.

English

NASA Technical Reports Server

December 1972
	 B72-10737 
NASA TECH BRIEF 
S	 Lewis Research Center 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual Copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
WIDEBAND WATTMETER FOR

INSTANT MEASUREMENT OF REAL POWER 
Probe 
n
Current 
transformer
Simplified block diagram of wideband wattmeter 
The Problem: 
The necessity to obtain information on the flow of 
electric power in nonlinear and time-varying systems had 
led to a number of attempts to devise wide-band 
wattmeters. Many switching and pulse circuits generate 
power spikes during their transition or switching time. 
This transient power may be of great significance and 
should be taken into account to avoid catastrophic 
failures in the active devices. Conventional sine wave or 
low frequency wattmeters are inadequate for this purpose. 
The Solution: 
A portable, solid state wattmeter with a wideband (dc 
to 1 MHz) linear multiplier which provides true four 
quadrant operation permitting instantaneous indication of 
real power as an oscilloscope display. 
How It's Done: 
As shown in the figure, amplifier Al is a differential 
voltage amplifier and with suitable range switching covers 
the 1 to 1000 volt range. A3 and A7 amplify the output
of Al to the desired 1 to 10 volt range and drive the 
multiplier X input. Amplifier A2 is a differential amplifier 
for the current shunt signal. It is followed by two single 
ended amplifiers, A4 and AS, which raise the signal level 
to the desired 1 to 10 volts for the multiplier Y input. 
When either the current sensing probe or the current 
transformer is used, only amplifier A5 is needed. Current 
input may be from the probe (0-10 amps), a shunt 
assembly, or a current transformer. One of the latter two 
items is necessary for the 10-100 ampere range. 
Accidental overvoltage or overrange protection is pro-
vided by fast recovery diodes and zener clamps. This 
facilitates measuring repetitive pulse waveforms where a 
portion of the signal is overrange. The portion of the 
signal which is within range will be accurately reproduced. 
Average power indication is provided by meter, Ml, 
and its associated driver, A6. The use of this meter in 
conjunction with external meters reading true rms voltage 
and current permits the determination of power factor for 
repetitive non-sinusoidal power waveforms. 
(continued overteaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000736 2020-03-17T03:44:03+00:00Z
Notes:	 - 
1. This wattmeter should be of use to manufacturers and 
users of semiconductors, transformers, inductors and 
capacitors which carry currents with abruptly changing 
waveforms. 
2. Performance specifications are: frequency band width 
dc to 1 MHz; current range 10 mA to 100 amperes 
peak; voltage range 1 volt to 1000 volts peak; accuracy 
±2% of full scale reading. 
3. The unit can be assembled in a volume no larger than 
20.3 cm x 25.4 cm x 20.3 cm (8 x 10 x 8 inches), and 
weighs no more than 4.5 kg (10 pounds). 
4. The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: NASA CR-72752 (N72-14420), De-
velopment of a Wideband Wattmeter as a Labora-
tory Instrument 
5. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72-10737 
Patent Status: 
NASA has decided not to apply for a patent. 
Source: L.G. Landes and Y.Y. Liu
Barnes & Reinecke, Inc. 
under contract to
Electronics Research Center 
(LEW-11698)
S 
. 
•1 
B72-10737	 Category 01


Wideband wattmeter for instant measurement of real power

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