fplenin 0 Posted July 17, 2014 Hi everyone Is there any "guide" or something about CCTV with "not to do" or "to avoid" things? (but I don't want something like: do not drop water over the dvr...you know...) It's because I've been thinking if there's any problem with certain things I usually do, like measuring impedance (or resistance, not sure about the word) with a multimeter to video and power cables (I do it with camera off -if checking power- or camera on or off while checking video). Today I was checking video cables and conectors (I checked them on video for impedance to see if the conector is working, then I plug it into the DVR), I did it with several cameras and one of them failed today, it was a pretty old camera but I'm not sure if I shouldn't do it and that caused it to fail or it was a coincidence. Sometimes I check for impedance to see if there's a video cable on short or broken (with the DVR on), if it's ok it will give a value from a few Ohms to a few hundreds Ohms, if it's on short it will give 0 or less Ohms, if it's broken, infinite Ohms... I just wanna be sure I'm not doing anything stupid that can damage a DVR, a camera or something... Thanks for your advice Share this post Link to post Share on other sites
mgb 0 Posted July 17, 2014 You should not use an ohm meter for resistance on any live circuit. I'm not sure why you check for this. Was video lost Share this post Link to post Share on other sites
fplenin 0 Posted July 17, 2014 Yep...I was testing new bnc compression conectors, first time doing them and I needed to check if it was in propper contact before crimping it (if resistance was equal measured with core vs mesh and then from center pin to outer BNC conector, it was in place). So, I did it with several cameras, no problem with any other. Could this have damaged the camera if it was on? A friend of mine told me that they should be able to handle "interference", such as a multimeter checking resistance with a pretty small current. And there was a camera that I was troubleshooting that had a video cable in short, and was a cheap one and worked that way for days, maybe weeks before I fixed it's video cable... I just wanna be sure about what things I really can do and what things shall never be done (that could damage camera, dvr, etc) Share this post Link to post Share on other sites
milkisbad 0 Posted July 17, 2014 Don't try to repair the camera yourself if you have to cut and splice a new power cable, it voids the warranty. (at least for the supplier that I work at) Share this post Link to post Share on other sites
fplenin 0 Posted July 17, 2014 No. It doesn't have any warranty. Neither I'm trying to fix it. BTW, I noticed that resistance when measured the first time started to increase, slowly going to infinite value of Ohms. Then I had to wait a few secs or minutes before resistance goed back to normal and start to slowly grow to infinite again... Share this post Link to post Share on other sites
mgb 0 Posted July 17, 2014 Metering it while hooked up won't necessarily blow anything. Usually on higher voltages and what not, it's more likely to damage your meter. It just doesn't make sense to meter for ohms on the line while its hooked up to the dvr. When I do connections, I carefully do them to avoid mistakes and then hook it up. If it doesn't work, then I redo the connection if needed. Share this post Link to post Share on other sites
fplenin 0 Posted July 17, 2014 Is it ok making bnc or video balun connections while DVR and cameras are on? offcourse, no messing arround with the 12v or 24v power cables when it's on...I perfectly know it. I measured ohms while video cable connected to DVR, got a (example) 200 ohm reading on a nearby camera, then tried the other one, got 0 Ohm, so, cable was is short. If there's no reading (ohms are infinite) it means there's a broken or unplugged cable. I'm talking about VIDEO cables... Share this post Link to post Share on other sites
Dirk_D 0 Posted July 18, 2014 Is it ok making bnc or video balun connections while DVR and cameras are on? offcourse, no messing arround with the 12v or 24v power cables when it's on...I perfectly know it. I measured ohms while video cable connected to DVR, got a (example) 200 ohm reading on a nearby camera, then tried the other one, got 0 Ohm, so, cable was is short. If there's no reading (ohms are infinite) it means there's a broken or unplugged cable. I'm talking about VIDEO cables... I wouldn't trust your readings. If you got a 0 ohm reading your meter is probably shot. Sounds like you need a little practice/tools/experience. First thing, if you want to test the cable, test the cable. Direct short at the far end (get a feel for it, you should get readings in ....I dunno, I don't test CCTV cables like this (but I test others) no higher than 10 ohms, or in that neighborhood for <200' runs....probably closer to 3-6 ohms. If you try to "test" the cable while it's connected to a camera, you're likely to get 300K-ohms to 1.5meg-ohms, again ballpark but useless #s. I think you'd do better to check the composite video signal voltage. should be ~1.4 VDC, peak to peak iirc I just pulled an analog bnc from an analog dvr to "test" the cable going to a camera, it read ~1.1vdc & ~1.3 meg-ohms. Share this post Link to post Share on other sites
fplenin 0 Posted July 19, 2014 Ok, I shall then get a 1.X volts DC from the camera video cable and thousands to million ohms (I'll asume I can not damage the camera by doing so) I'm thinking on getting an Uni-T digital multimeter with amps reading also. I currently have an OOOOOOOld analog multimeter (helped me lots of times with troubleshooting). I like to keep getting knowledge and propper tools to make things faster and better everyday. Do you have any advice on multimeters? Share this post Link to post Share on other sites
Dirk_D 0 Posted July 19, 2014 I bet you'd be happy with the uni-t, I have 2 of their meggers, and then I also picked up their UT81B scopemeter last year just for fun. I don't know your use/budget, there's lots of options.... the next "cheap" multimeter I wanted to get was the BK precision 2709B but I don't think it's as protected as the flukes (I have lots of yellow & gray meters floating around). I bet you'd like the Fluke 115, I got one for one of the guys that.....I didn't care so much if it got lost. They're (fluke) padded, reliable, and maybe not the absolute best, but they're an easy choice. http://www.amazon.com/Precision-2709B-Auto-Ranging-Multimeter-Millifarads/dp/B004O8Z89C/ref=sr_1_1?ie=UTF8&qid=1405732352&sr=8-1&keywords=bk+precision You can waste a lot of time reading/watching reviews: I bet a lot of the guys here have some reliable ways to test coax..... hopefully someone else will chime in. Share this post Link to post Share on other sites
fplenin 0 Posted July 19, 2014 Well, I live in Venezuela, it's a pain in the ass to buy expensive stuff...But I also like tools that lastes and doesn't need me to be careful about them...but I can't afford any "top tool", because things get "lost" easily here...crime here is like a normal thing to see or hear about everyday... Also, I'm not a electronics tecnichian (not sure if that's the name you give to them), I wouldn't mind to lose 0.5% precision for 30% of the price...you know...Just want a quality and reliable tool that can read amps, ohms, continuity and volts, I'm not trying to fix a video card or mod a camera to microscope lol...you know what I mean Share this post Link to post Share on other sites
fplenin 0 Posted July 19, 2014 UNI T prices are about half as a fluke...and also measures amps with it's clamp...but sincerely I'm not sure if they are durable Share this post Link to post Share on other sites
fplenin 0 Posted July 19, 2014 great review, thanks. But I need a clamp also...it can be pretty useful to me because I sell UPS and people might ask "how much Watts do I need?" or even would let me work with simple electrical stuff, like AC wiring and breakers. http://www.amazon.com/Fluke-323-True-RMS-Clamp-Meter/dp/B00AQKIEXY/ref=sr_sp-atf_title_1_1?ie=UTF8&qid=1405775803&sr=8-1&keywords=fluke+clamp This seems pretty nice for the price, but only measures 40 KOhm...it wouldn't be so useful for CCTV camera testing, would it? Share this post Link to post Share on other sites
mgb 0 Posted July 20, 2014 I like Flukes. The 115 is a good a around model with true rms. I've had my 112 for a good ten years. You can also get coax and cat testers. Share this post Link to post Share on other sites
