Low cost method is described for signal conditioning of pot-type transducers utilizing printed circuitry. Conditioner fits into standard rack, accommodates 56 channels, and can be operated by one attendant

Armentrout, E. C.

Gross, E.

English

NASA Technical Reports Server

March 1973
	 B73-10015 
NASA TECH BRIEF 
•	 Lewis Research Center 
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commerca application Tech Brets are aaIable on a subscription oasis from the National Techrr cal Information 
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be crectec to the Technic ogy Utlizaton Office NASA, Code KT. Washington, 0 C 20546 
SIGNAL CONDITIONER FOR
POTENTIOMETER TYPE TRANSDUCERS 
-	 .
W ill 
All fill 
^ 0!", 1, ^ I ,.	 -J: to -J I 
OL 
.
FIGUhL 1 
The Problem: 
The method employed in most test cells for signal 
conditioning of pot-type transducers is individual adapta-
tion of available parts assembled by a technician when the 
need for such a conditioner arises. It usually occupies 
considerable panel space and/or is so located that two 
technicians are required to adjust and read the meter or 
chart. 
Two commercial signal conditioners are available. One 
is a 20 channel conditioner which is merely a regulated 
power supply. The zero and span adjustments must be 
added to the transducer as options. The cost per channel 
for this 20-channel conditioner is approximately $80. This 
conditioner does not provide the convenience and ne-
cessity of adjustment from the control room. The other 
commercial signal conditioner is a strain-gage type signal 
conditioner which costs approximately S 125. per channel.
The Solution: 
A pot-type signal conditioner utilizing printed circuitry 
which fits into a standard 17.8 cm (7 inch) by 48.3 cm 
(19 inch) rack, accomodates 56 channels, can be operated 
by one attendant, and costs approximately $45. per 
channel (see Figure 1). 
How It's Done: 
The pressure transducer used in this system employs a 
capsule or a bourdon tube as the sensing element. Figure 2 
is a schematic diagram. A frictionless lever system 
amplifies the motion of the sensing elements and operates 
a contact wiper over a potentiometer, thus the resistance 
change is proportional to the input pressure change. An 
external power supply, considered part of the signal 
conditioner, provides a dc voltage across the poten-
tiometer. The output from the wiper is fed into a high 
impedance readout device. 
40 -	 (continued overleaf) 
This document was prepared under the sponsorship of the Natona 	 Government assumes any iab. i ,ty resulting from the use o f
 the 
Aeronautics and Space Administration Nether the Unted States 	 niormation contaneo 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=19730000015 2020-03-17T06:38:40+00:00Z
115V 60'\.i
Signal cond. 
Power
 
supply
F i1 ITi 
Transducer 
Read out 
Figure 2 
In order	 to provide some adjustment of the zero Note: 
reading and full scale or span, the transducer may be Additional documentation may be obtained from; 
purchased with a span	 pot	 and zero bypass wiring. Technology Utilization Officer 
Locating the adjustment on the transducer itself is not Lewis Research Center 
always the most convenient location, however. Locating it 21000 Brookpark Road 
back on the power supply converts the power supply into Cleveland, Ohio 44135 
a single channel signal conditioner, as is done in this unit. Reference: B73.10015 
In	 addition,	 current	 limiting	 resistors	 are	 added	 to 
improve	 the	 overall	 readout accuracy. The	 pot-type Patent Status: 
transducer normally has a resistance of only 1000 ohms, NASA has decided not to apply for a patent. 
so that there is some current flow which creates an 
inaccuracy, but this type transducer may be used when a Source: E.C. Armentrout and E. Gross 
1-2% readout is adequate. Lewis Research Center 
The design of this unit not only provides conveniences (LEW-1 1822) 
and	 ease	 of operation,	 but	 the	 cost	 per	 channel is - 
one-third	 to	 one-half that	 of commercially	 available 
equipment.
B73-10015	 Category 01	 0 


Signal conditioner for potentiometer type transducers

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