Yes, I believe so, but others here know more, from what I've read. I=20 recall using commercial current probes from tektronix.=20 > =20 for low current, high speed measurements. With the SCT-013 I've observed nice waveforms of 60 Hz current at about=20 1 amp in the primary. I imagine it would be high frequency you'd be=20 concerned with in a triac circuit. Joe W On 11/14/2011 3:43 PM, KPL wrote: > wil CT's provide output signal more or less same form as the current? > I mean, are they usable to use as current pickups for scope, when > testing triac-regulated circuits? I'm just not sure how ferrite works > with these low frequencies. > I do not need to measure amplitudes, just to see the angle when triac > is switched on. > That would be much easier than using big isolation transformer before > whole circuit. > > On Mon, Nov 14, 2011 at 17:42, Joe Wronski w= rote: >> Not much technical info here, but there are some sources of CTs and >> examples of biasing, etc. >> >> I bought CTs with and without internal burden resistors from >> seeedstudio. I use the unburdened one to simply detect lower currents, >> but might need an op amp for any accuracy with a burden R. Using a >> freebie ferrite core is tempting, but I like the clamp on method the >> SCT-013 units use. I've seen how-to's of making your own calmp on using >> a ferrite core and a big alligator clip. >> >> Joe W >> >> >> >> >> On 11/14/2011 5:56 AM, Isaac Marino Bavaresco wrote: >>> Em 14/11/2011 03:12, Grant Tudor escreveu: >>>> Issac, >>>> >>>> There is a low temperature alarm hence the desire to have a battery ba= ck up >>>> so that the unit can sense when there is a mains failure. This works w= ell >>>> if both elements have failed or the door is left ajat etc as you menti= oned. >>>> >>>> The idea of the current drawn indication is to show that elements are >>>> working (or not). The incubator has two heating elements for redundanc= y. >>>> Either is sufficient to heat the incubator to the required temperature= .. The >>>> problem is that it may be possible for one element to sop working and = you >>>> would not notice it because there is no indication that it is working = or >>>> not. The second element would then take over the heating of the incuba= tor >>>> but the redundancy is no longer there. If the second element stops wor= king >>>> then there is a potential catastrophe. If there is still power, the lo= w >>>> temperature alarm will sound but if may be a while before anyone is ar= ound >>>> to hear it. If I had an indication that one of the element had stopped >>>> working then the element could be replaced and redundancy restored. >>>> >>>> I like the ferrite core concept as it is simple, easy to retrofit and >>>> provides a level of isolation between the LV circuit and the 240VAC. I= just >>>> need to get the voltage up to a sufficiently high level to be workable= .. I >>>> could then either monitor the voltage using the PIC directly, or use t= he >>>> voltage to light a LED to provide a visual indication that the element= is >>>> working. >>>> >>>> R/- >>>> >>>> Grant >>> You could amplify the signal with an Op-Amp as I suggested in my >>> previous post or you could offset the signal to VCC/2 and measure the >>> sinusoid directly with the A/D converter of the PIC. >>> >>> You told that you got an 100mV signal. That is 200mVpp. If you offset >>> the signal to 2.5V then you would get 2.4V in the negative semi-cycle >>> and 2.6 V in the positive semi-cycle. That would give a differential >>> reading in the ADC of 40 counts, this may be enough to detect that the >>> heater is consuming power and even how many heater elements are working= .. >>> >>> >>> Best regards, >>> >>> Isaac >>> >> -- >> http://www.piclist.com PIC/SX FAQ& list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> > > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .