Batteryless current clamps?
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From: Tim Williams on 17 Nov 2009 10:20 On Nov 17, 2:18 am, Fester Bestertester <f...(a)fbt.net> wrote: > I'm curious how the Fluke i200s current clamp probe can give mV output > without the use of batteries. Is that the one with the 10/100 switch and a green LED? I'm pretty sure most of the weight is not ferrite, it's a battery somewhere. They also read DC, and have an offset knob to account for the ferrite's hysteresis. The passive probes only read AC, and as I recall, are 1 or 10 mV/A. Tim
From: John Fields on 17 Nov 2009 10:29 On Tue, 17 Nov 2009 05:39:40 -0800 (PST), Bill Sloman <bill.sloman(a)ieee.org> wrote: >Unhelpful abuse counts as a waste of bandwidth. > >Raise you game or expect to be plonked. But don't worry if Jim >Thompson plonks you - he plonks everybody who disagrees with him, >which is probably one of the reasons he believes so many things that >don't happn to be true. --- Typical Slomanesque two-faced rhetoric; you damn unhelpful abuse as a waste of bandwidth and then, in the same breath, engage in it yourself. JF
From: pimpom on 17 Nov 2009 10:56 Fester Bestertester wrote: > I'm curious how the Fluke i200s current clamp probe can give mV > output > without the use of batteries. > > How is this done? If one is measuring 200A I can see how the > magnetic > field could generate enough current in the probe to support > some > high-impedance, low-draw circuitry. > > But when measuring on the low scale, say, 2 or 3 amps, how > could the > probe output a few hundred mV? (The clamp is spec'd to output > 100mV / > amp on the 20A low scale, 10mV on the 200A high scale.) > > Can someone explain this to me? I'm fascinated to see it's > possible & > curious to know how. > You seem to have a preconceived notion of what constitutes large, small and insignificant currents levels in terms of the fields they generate, but such categorisations are only relative. "2 or 3 amps" is quite huge in some contexts and generate an appreciable flux in the magnetic core of the clamp. The alternating magnetic field induces a voltage in the clamp's pickup coil and this voltage can certainly reach "a few hundred mV" if enough number of turns are used. You can also think of the clamp as a current transformer. The wire being measured for current is the primary and the pickup coil of the DMM is the secondary. If you're more familiar with voltage transformers, think of it this way: Suppose you have just 1 mV output from a microphone. Connect it to the primary of a 1:10 transformer and you will get 10 mV at the secondary terminals. Use a 1:100 transformer and you get 100 mV and so on, theoretically up to any voltage.
From: bud-- on 17 Nov 2009 10:59 Bill Sloman wrote: > > Unhelpful abuse counts as a waste of bandwidth. > > Raise you game or expect to be plonked. Please ignore the ignorant troll that infests alt.engineering.electrical.
From: John Larkin on 17 Nov 2009 11:25
On Tue, 17 Nov 2009 02:46:44 -0800 (PST), Proteus IIV <proteusiiv(a)gmail.com> wrote: >On Nov 17, 3:18�am, Fester Bestertester <f...(a)fbt.net> wrote: >> I'm curious how the Fluke i200s current clamp probe can give mV output >> without the use of batteries. >> >> How is this done? If one is measuring 200A I can see how the magnetic field >> could generate enough current in the probe to support some high-impedance, >> low-draw circuitry. >> >> But when measuring on the low scale, say, 2 or 3 amps, how could the probe >> output a few hundred mV? (The clamp is spec'd to output 100mV / amp on the >> 20A low scale, 10mV on the 200A high scale.) >> >> Can someone explain this to me? I'm fascinated to see it's possible & curious >> to know how. >> >> Thanks. > >CURIOUSITY KILLED THE CAT >GO TO SCHOOL AND HEAR IT FROM THE HORSES NOUTH > >OR GO TO YOUR NEAREST TECHINAL BOOK STORE AND PURCHASE TEST METERS >FOR DUMMIES > >I AM PROTEUS Hey, it's been too long. The only time we hear from you is when your kid sister kicks you off the Xbox. John |