about Clamp and DC, there are 2 kind of clamp. some are pure AC transformers, with good AC bandwidth (up to MHz). some are hall effect, with DC sensibility, but moderate bandwidth (few kHz), and very expensive.
it seems the PCE830 clamps are AC only... maybe a bad choice for that test... I have never seen the model of the current clamps. The specification of the PCE-830 depend on the clamp used. anyway if you don't fear an unusual main AC power this would be a very good instrument. 2013/6/26 Jed Rothwell <[email protected]> > Abd ul-Rahman Lomax <[email protected]> wrote: > > >> First of all, the clamp-on probes used with the PCE-830 cannot measure DC >> current > > > I don't know about this one, but my 30-year-old analog Radio Shack > clip-on ammeter sure can measure DC. You turn the knob to DC and it works > fine. > > > >> They operate through sensing the changing magnetic fields from changing >> current in the wires. DC, no change. >> > > My point is that as long as it reverses it is AC and will be detected. > Adding DC voltage just adds a bias. It does not make the AC go away. > Unless, as noted, you add so much that it stays positive. > > > >> Secondly, the PCE meter not being designed to measure DC power -- no DC >> current sensors -- . . . > > > If it cannot read a DC bias it is useless. I am sure it can. They all > could 40 years ago. > > > >> (You are assuming a single solid-state "switch" in the control box, so >> that AC and DC turn on and off together. But the AC and DC could be >> isolated, separated, essentially a DC bypass.) >> > > It is one wire. How do you keep them separated?!? > > > >> This makes the second such failure to understand test equipment on the >> part of Essen. The first was the humidity meter. Did you ever understand >> that one? >> > > Sure. I looked at the manual and contacted the manufacturer, and they > said that meter with that probe works fine for that purpose. It says it > measures the enthalpy of steam. I don't know why you think it doesn't when > the manual and brochure clearly state that it does. > > I admit, I tend to take for granted whatever the manufacturers' say. If > they say "this meter measures the enthalpy of steam" (the wetness) I assume > they are right. The PCE company would not stay in business long if any high > school kid could find a way to fool their meters, or if the meter indicated > a wire is dead when it is alive. > > Recently, Shanahan said that IR cameras do not measure temperatures > correctly. He gave a long list of theoretical reasons. I pointed out that > the manufacturer sells these things to measure temperature, and millions of > engineers use them for that purpose, plus Levi compared this one to a > thermocouple, so I am sure Shanahan is wrong. > > - Jed > >
