Bistable amplifier prevents damage in the low range circuitry of a dual scale ammeter. It senses the current and switches automatically to the high range circuitry as the current rises above a preset level

Iceland, W. F.

English

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Ik	 JL1 91	 I 
I Bistable 
i Amplifier 
L— — — —J 
September 1970	 Brief 70-10392 
NASA TECH BRIEF	 4 N_X lj
^ 
NASA Tech Briefs announce new 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 Clearinghouse for Federal Scientific and Technical 
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be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
- .	
.-.----	 --	 -	 -. 
Dual Current Readout for Precision Plating 
Negative(	 Negative 
Lead In	 30A
	
Lead Out 
I	 300mV (4 Places)	 +
Ampere Hour 
Meter i)	 () KlA 
0-30	
R3I 
0-300 I 
mmeter	 R4
Ki B
1 lOVac 
24Vd' T" T T 
- 
Si 
The problem: 
In a precision electroplating system it is necessary 
to read precisely the current drawn by means of a 
single, dual scale (0 to 30 and 0 to 300) ammeter. In 
this application, the lower scale portion of the meter 
must be protected when the current drawn exceeds 
30 amps. 
The solution: 
Use of a bi-stable amplifier to prevent damage in 
the low range circuitry by sensing the current and
automatically switching to the high range circuitry 
as the current rises above a preset level, in this case 
30 amps. 
How it's done: 
In operation, 115 V ac is applied through- switch SI 
and is rectified in series with resistor RI (See fig.). 
This voltage is filtered and regulated through zener 
diode Dl and applied to terminals 3 and 4 of the bi-
stable amplifier. The negative lead-in is attached to 
the plating power supply (not shown), and the negative 
(continued overleaf) 
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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=19700000378 2020-03-17T00:43:30+00:00Z
lead out is connected directly to the plating solution 
cathode. As current flows through the solution, it 
also flows through the four 30 amp, 300 mV shunts 
and the ampere-hour meter. Current flowing through 
the 0 to 30 amp circuit of the dual scale ammeter is 
controlled by the coil of relay Ki. The two contacts 
K1A (normally closed) and K1B (normally open) 
are actuated as the plating current exceeds 30 amps. 
Resistor R2 controls the level of operation of the bi-
stable amplifier by limiting the current flowing 
through terminals 5 and 6. As relay Kl is actuated 
through terminals 1 and 2 of the bistable amplifier, 
the dual scale ammeter is calibrated through resistors 
R3 and R4, which are (individually) in series with 
the meter. The ampere-hour meter provides current-
time totals and may be reset by an external control 
knob.
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Manned Spacecraft Center, Code BM7 
Houston, Texas 77058 
Reference: B70-10392 
Patent status: 
No patent action is contemplated by NASA. 
Source: W.F. Iceland of

North American Rockwell Corporation

under contract to

Manned Spacecraft Center

(MSC-15673)
. 
. 
. 
Brief 70-10392	 Category 01


Dual current readout for precision plating

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