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breadboard component; press to break/make circuit and measure current

O

oldyork90

Jan 1, 1970
0
I have a breadboard circuit that requires multiple and frequent
current measurements. Is there a breadboard component that can break
and make current measurement connections using a probe?

The action would be, the circuit is broken as the current meter probe
presses down on an isolated conductive surface (part of this current
"tap" switch). After the circuit is broken, further travel connects
this isolated conductive surface to the input circuit. The circuit is
now complete again, this time with the current meter in series.

The circuit would suffer a momentary loss of input, but that is of no
concern. I could build this, but was hoping there was a nice little
proto compo I could use.

Thank you.
 
J

John Devereux

Jan 1, 1970
0
oldyork90 said:
I have a breadboard circuit that requires multiple and frequent
current measurements. Is there a breadboard component that can break
and make current measurement connections using a probe?

The action would be, the circuit is broken as the current meter probe
presses down on an isolated conductive surface (part of this current
"tap" switch). After the circuit is broken, further travel connects
this isolated conductive surface to the input circuit. The circuit is
now complete again, this time with the current meter in series.

The circuit would suffer a momentary loss of input, but that is of no
concern. I could build this, but was hoping there was a nice little
proto compo I could use.

I assume you know about clamp-on current meters / probes?
 
N

Neon John

Jan 1, 1970
0
I have a breadboard circuit that requires multiple and frequent
current measurements. Is there a breadboard component that can break
and make current measurement connections using a probe?

Yes. It's called a diode. Place a diode between your test points so
that it is forward biased. It will drop about 0.7 volts under normal
conditions. 0.3 volts or so for a Schottkey diode.

When you attach your ammeter probes to the test point, the meter's
current shunt, which drops far less than 0.7 volts, now conducts all
the current and the diode turns off. Just make sure that your test
leads are heavy enough not to drop significant voltage.

Using this method there is no interruption of the circuit, not even a
glitch as the meter is connected and disconnected.

John
John DeArmond
http://www.neon-john.com
http://www.fluxeon.com
Tellico Plains, Occupied TN
See website for email address
 
W

whit3rd

Jan 1, 1970
0
I have a breadboard circuit that requires multiple and frequent
current measurements. Is there a breadboard component that can break
and make current measurement connections using a probe?


The action would be, the circuit is broken as the current meter probe
presses down...

Sure, just put in a momentary contact NC pushbutton. It has
to be normally closed (NC) so the current meter can be unplugged.

To make a current reading, plug in the current meter (across the
switch) and push the button, then read the meter.

The voltage burden on the meter may allow other switch types (like a pass diode),
or you might be able to do Hall effect measurements of DC current in a wire loop, but
those get into accuracy and functional and cost tradeoffs.
 
O

oldyork90

Jan 1, 1970
0
Sure, just put in a momentary contact NC pushbutton.  It has
to be normally closed (NC) so the current meter can be unplugged.

To make a current reading, plug in the current meter (across the
switch) and push the button, then read the meter.

The voltage burden on the meter may allow other switch types (like a passdiode),
or you might be able to do Hall effect measurements of DC current in a wire loop, but
those get into accuracy and functional and cost tradeoffs.

Went with the momentary. Thank you. Good suggestion.
 
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