[Boatanchors] "Clamp-On Ammeter" question

[Robert Bethman]

Hi Phil,

I guess I'm an antique.  I have owned an industrial Weston Clamp-on Ammeter since the latter half of the '70s.  Obviously it is analog.  The low range is 0 to 6A.  I can't imagine not having it on the bench.

I'll grant that it hasn't been calibrated in a very long time.  But I have checked it against known systems, and it is extremely close to the actual value.

I did have the chance to go side by side with an air conditioner technicians Fluke.  If it is off any, I couldn't see it.

It also has a set of leads that plug into the base of it and allows AC and DC voltage reading ability.

The voltage part of it agrees with my HP-410B and the TS-505D/U.  I didn't see a reason to run it against my DMM.

I wouldn't let it out of here for anything!

Regards, Bob - N0DGN

-----Original Message-----
From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Phil
Sent: Thursday, May 19, 2016 3:06 PM
To: Boatanchors <boatanchors at mailman.qth.net>
Subject: [Boatanchors] "Clamp-On Ammeter" question

Hi All,

In the past, if I needed to measure the current draw of a device, I removed the fuse (if it had one) and put one of my DVMs, set to measure current across the fuseholder.  IF no fuse then I jury-rigged a test setup.

Today I bought one of those whiz-bang clamp-on ammeters that Harbor 'Fright' sells  (the 'big' one, $13.59 after the 20% coupon).  Yeah, I know, they're not lab grade, but should be better than nothing.  I also realize that with the "transformer coupling" the clamp-on feature is only for AC.

I intend to modify my DBT (Dim Bulb tester) to use as an interface between the Isolated Variac and the DUT by installing a small DVM (one of the "freebie" Harbor Fright meters) in the DBT and a switchable "loop of wire" for the clamp-on in parallel with the light socket.  This way I can simultaneously monitor both the Voltage and current draw of the DUT.

The clamp-on meter I bought has three ranges, 20, 200 & 1000 Amps, all a bit high for testing the primary current draw of the typical radio item.

Here comes the question:  In old age the brain cells regarding the most basic radio theory I learned as a child seem to have self erased.  In transformer coupling, I 'think'  it's one for one. That is, IF I put a coupling loop of two turns in the primary lead of the DUT and clamp the meter over that double loop, the sensitivity of the meter would double.  
That is, instead of a 20Amp range, it would then be a 10 amp range.  4 Turns would change a 20 Amp range into a 5 Amp range.

DO I HAVE THINGS RIGHT, or do I have it backwards??  Inquiring minds want to know. . .


-- 
73 From "The Beaconeer's Lair"
Phil, KO6BB
http://www.qsl.net/ko6bb/  (Web Page)

HF/LF RADIOS:
Grundigs: S-350 (~2006), G6 (2011) & S450DLX (2014).
HOMEBREW: 7 Tube+Rect 1v3 Regenerative RX for LF (built 2015)
Icom:     IC-735 Transceiver (~1990).
Icom:     R-75, Cascaded 250/125Hz CW-Filt, Panadapter. (~2009)
Icom:     IC-7200 Transceiver (~2015).
R-Shack:  DX-380 digital portable (~1990).
SDR:      Softrock Ensemble II LF (built from a kit 2015).
Zenith:   Royal-7000 Transoceanic Portable (~1968).

ACC:   HOMEBREW  LF-MF Pre-Amp, MFJ-993B HF Auto-Tuner.
        HOMEBREW  4 Port Multicoupler, Feeds Antenna to 4 RX's.
        HOMEBREW  8 Hz Audio Filter.
        Timewave  DSP-599zx Audio Filter.
        Behringer 1202fx Audio Mixer (for mixing/routing audio).

ANTENNAS: 88 foot Long Ladder-line fed dipole, 35 feet AGL for MW/SW.
           Active Mini-Whip, 36 Feet AGL for LF/MW/SW.
           37 foot "Low Noise Vertical", 11 feet AGL for LF/MW/SW.

Merced, Central California, 37, 18, 37N   120, 30, 6W CM97rh

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