Thanks for all the great information. I have ordered a couple of the Seeed Studio current sensors and I will get back to the list when I have had a chance to try them out. Regards, Grant On Tue, Nov 15, 2011 at 12:12 PM, Joe Wronski w= rote: > Yes, I believe so, but others here know more, from what I've read. I > recall using commercial current probes from tektronix. > < > http://www.tek.com/products/accessories/current.html?WT.srch=3D1&WT.mc_id= =3Dppc,covtekggl91000000014973s > < > http://www.tek.com/products/accessories/current.html?WT.srch=3D1&WT.mc_id= =3Dppc,covtekggl91000000014973s > >> > for low current, high speed measurements. > With the SCT-013 I've observed nice waveforms of 60 Hz current at about > 1 amp in the primary. I imagine it would be high frequency you'd be > 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 > wrote: > >> 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 usi= ng > >> 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 > back up > >>>> so that the unit can sense when there is a mains failure. This works > well > >>>> if both elements have failed or the door is left ajat etc as you > mentioned. > >>>> > >>>> The idea of the current drawn indication is to show that elements ar= e > >>>> working (or not). The incubator has two heating elements for > redundancy. > >>>> 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 an= d > you > >>>> would not notice it because there is no indication that it is workin= g > or > >>>> not. The second element would then take over the heating of the > incubator > >>>> but the redundancy is no longer there. If the second element stops > working > >>>> then there is a potential catastrophe. If there is still power, the > low > >>>> temperature alarm will sound but if may be a while before anyone is > around > >>>> to hear it. If I had an indication that one of the element had stopp= ed > >>>> working then the element could be replaced and redundancy restored. > >>>> > >>>> I like the ferrite core concept as it is simple, easy to retrofit an= d > >>>> 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 > the > >>>> 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 th= e > >>> 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 > >> > > > > > > -- > 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 .