Electronic circuitry is devised to raise low level signal from platinum film type transducer to sufficient amplitude to trigger oscilloscope or time interval counter. Circuit can be used wherever it is necessary to raise level of low amplitude, low impedance positive polarity pulse source to a 5 or 6 volt level

Jensen, K. A.

English

NASA Technical Reports Server

August 1972	 B72-10463 
NASA TECH BRIEF 
Lewis Research Center	
£ A 
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. 
Amplifier for Signal from Thin Film Transducer 
Bias
Milliemmeter
0-15 F.S. 
-r'+ MAP—,	 r_®__1u1h11__1 Optional 
Battery 
IBA Bias n &;0^0 
(Pi)	 (PI) 
	
_____	 —12V 
5'	 B TA 
_1t_	 Power Input 
0.0O1
	
T D(	
Connector
 
1K	
JJ')
25W 15p I 
	
lOT	
680
00 5JJF 
1	 Adjust	 1%	 0.15w	 1%	
12	 ' 
Thin Film	 25FF
180K 
	
Bias	 15K	 1500 25V 
25F	 )I-	 38,3K'j25V 1500
CA3015A 
	
o.i	 23 
) I
	
	
21	 .>____ -If 2N29
+12V	
B 
Pulse 0.47w	 Output FOK)J2)
6	 — 100V
	
120	 RG-62/U Cable 
O PF I I	 15K 
	
120	 1 
+
25;F
-12V	 - 
(]	
1500	
- 
25V  
38.3K 
Thin Film	 .1  1% 
	
Transducer	 Resistors 1/4 Watt Unless Noted Otherwise, All Values Are in Ohms 
100 to 300 Ohms 
Electronic circuitry has been devised to raise the low 
level signal from a platinum film type transducer to a 
sufficient amplitude to trigger an oscilloscope or time 
interval counter. This amplifier has been used with shock 
tube apparatus to measure wave velocity between two or 
more points, and also to generate a timing signal to 
trigger an oscilloscope. The circuit could be used where. 
ever it is necessary to raise the level of a low amplitude, 
low impedance positive polarity pulse source to a 5-or 6-
volt level.
The delicate construction of the thin platinum film 
transducer necessitates a low value of bias current, thereby 
limiting the available output signal. The circuit shown in 
the figure overcomes this problem and delivers the signal 
suitable for the shock tube  measure men ts.The input circuit 
biases the transducer at one to ten milliamperes; this is 
adjustable and determined by the thin film characteristics. 
Power for biasing is normally drawn from the amplifier 
supply, but with the connections shown, an optional 
battery supply may be used. 
O
(continued overleaf) 
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=19720000462 2020-03-17T03:39:16+00:00Z
The first stage is a buffer amplifier providing slight 
gain-and signal polarity inversion. The next stage is an 
operational amplifier designed to differentiate the ampli -
fied pulse and restore the original signal polarity. This 
amplifier has a rise time of 0.5 microsecond and a voltage 
gain of about 3000. Short leads, adequate power supply 
bypassing, and grounding are important. The final stage 
is an emitter follower biased slightly less than cutoff to 
pass all positive polarity 6-volt peak signals. The entire 
assembly was mounted in a 3 x 4 x 2 inch (7.6 x 10.2 x 
5.1 cm) box installed directly on the transducer.
Note: 
No further documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72-10463 
Patent status: 
No patent action is contemplated by NASA. 
Source: K. A. Jensen
Lewis Research Center

(LEW-1 1494) 
B72-10463	 Category 01


Amplifier for signal from thin film transducer

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