hey everyone first time poster and hopefully long time learner from everyone here! a day or so ago my lcr meter was showing the correct cap values etc but now for some reason it will show a 470uf cap as 428uf and i am not sure why, i have calibrated it several times but so far no dice, does anyone know what i could do to try and fix this? also these caps are brand new never used
What's the tolerances of the caps?
428 uF for a specified 470 uF is a deviation of 8.9%, well within the typical ±20% for electrolytic caps and also within the tighter ±10% tolerance that is offered for the better ones.
so something like that should be normal then? i hope so cause was reading them at about 450uf before so i am not sure why its showing lower now
Hi Ironsniper, welcome to the forum! A dedicated LCR meter (I haven't got the DER5000 but an Applent AT826, yet for practical applications they should be comparable) offers many parameters that may actually affect the measurement results. First of all, it's always a good idea to use kelvin (four-wire) probes to measure the voltage directly at the terminals of the DUT and eliminate the resitance of the probes/connections themselves. Moreover, the measurement frequency has a major effect on the results. Especially electrolytics will show a considerable dependency while small plastic foil (particularly polypropylene/polystyrene) caps are almost independant. In case of the electrolytic caps, the temperature of the DUT also may have considerable effect, though this affects more the ESR than capacity. Electrolytics are usually specified at 120Hz measurement frequency, so please make sure you select something in this range.
Cheers,
Thomas
Hi Ironsniper, welcome to the forum! A dedicated LCR meter (I haven't got the DER5000 but an Applent AT826, yet for practical applications they should be comparable) offers many parameters that may actaully affect the measurement results. First of all, it's always a good idea to use kelvin (four-wire) probes to measurent he voltage directly at the terminals of the DUT and eliminate the resitance of the probes/connections themselves. Moreover, the measurement frequency has a major effect on the results. Especially electrolytics will show a considerable dependecy while small plastic foil (especially polypropylene/polystyrene) caps are almost independant. In case of the electrolytic caps, the temperature of the DUT also may have considerable effect, though this affects more the ESR than capacity. Electrolytics are usually specified at 120Hz measurement frequency, so please make sure you select something in this range.
Cheers,
Thomas
just checked the frequency and it was not set correctly, i changed it to 120hz and now its reading like it should and my kelvin clip upgrade is working perfectly! thanks everyone!
just checked the frequency and it was not set correctly, i changed it to 120hz and now its reading like it should and my kelvin clip upgrade is working perfectly!
Yes, electrolytic capacitors often read VERY differently when tested at different frequencies. The displayed value goes up as you raise the test frequency.
Enjoy the 5000; it's a useful tool.
... The displayed value goes up as you raise the test frequency.
Enjoy the 5000; it's a useful tool.
Really? I always found it to be the other way round, i.e. the higher the test frequency, the lower the measured capacitance will be. This also makes more sense from a theoretical point of view: Since some of the (AC) current flowing though an electrolytic capacitor is in forms of ion current, i.e. the physical movement of atoms (dissolved in the electrolyte), there will be some kind of "inertia" to put it simple and better imaginable. And this ion current won't follow the high frequency as easily as it will lower frequencies, hence the lower capacitance.
Cheers,
Thomas
Same here, go higher in measurement frequency results in a lower capacitance.
Capacitor Nippon Chemicon SXE 100uF 35V test on a ZXP ZX8511D with OPEN/SHORT calibration before the measurement:
On 100Hz
On 120Hz
On 1KHz
On 10KHz
Please note that the ESR on 120Hz is the highest and that is is much lower on higher frequenciies.
Step 1. Get capacitor datasheet.
Step 2. Read capacitor datasheet.
Step 1. Get capacitor datasheet.
Step 2. Read capacitor datasheet.
Step 3. Measure with the signal's specification "according" to the datasheet.