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| TH2830 vs TH2832 |
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| Martin72:
--- Quote --- You NEED to measure them at that frequency to compare capacity to nominal.. At 100kHz 1000uF represent miliohms and is hard to measure. --- End quote --- And still there a people in the forum who don´t want to understand this or can´t. It makes no sense measuring µF at 100khz, but they do and ranting about the "crappy meter"... @nctnico: This were my thoughts after reading the cal-protocol and wonder why they did´t test anything above 1kHz/10kHz, although the meter goes up to 100kHz. |
| KungFuJosh:
--- Quote from: nctnico on July 09, 2023, 11:40:11 am ---One thing to keep in mind when using an LCR meter is that the reading depends on measuring amplitude and phase. At some point these measurements can no longer be made with a reasonable accuracy. Most LCR meters have a graph or formula in the manual that tells you what kind of accuracy to expect for a given component value. Looking at the calibration results, you can see they don't bother measuring 100k Ohm at 100kHz and the 30k Ohm allows for a larger error margin compared to the measurement at 10kHz. --- End quote --- --- Quote from: Martin72 on July 09, 2023, 02:43:10 pm ---@nctnico: This were my thoughts after reading the cal-protocol and wonder why they did´t test anything above 1kHz/10kHz, although the meter goes up to 100kHz. --- End quote --- I think it's got more to do with either laziness or reducing the labor cost of calibration, and/or possibly whatever is actually required for specific cal standards. The Tonghui cal didn't measure less than 100pF at 1kHz, they didn't measure capacitance below 100Hz at all, and they didn't measure beyond 1nF, 10nF, 100nF at any range besides 1kHz. That's clearly not about machine capability. |
| nctnico:
--- Quote from: KungFuJosh on July 09, 2023, 04:08:29 pm --- --- Quote from: nctnico on July 09, 2023, 11:40:11 am ---One thing to keep in mind when using an LCR meter is that the reading depends on measuring amplitude and phase. At some point these measurements can no longer be made with a reasonable accuracy. Most LCR meters have a graph or formula in the manual that tells you what kind of accuracy to expect for a given component value. Looking at the calibration results, you can see they don't bother measuring 100k Ohm at 100kHz and the 30k Ohm allows for a larger error margin compared to the measurement at 10kHz. --- End quote --- --- Quote from: Martin72 on July 09, 2023, 02:43:10 pm ---@nctnico: This were my thoughts after reading the cal-protocol and wonder why they did´t test anything above 1kHz/10kHz, although the meter goes up to 100kHz. --- End quote --- I think it's got more to do with either laziness or reducing the labor cost of calibration, and/or possibly whatever is actually required for specific cal standards. The Tonghui cal didn't measure less than 100pF at 1kHz, they didn't measure capacitance below 100Hz at all, and they didn't measure beyond 1nF, 10nF, 100nF at any range besides 1kHz. That's clearly not about machine capability. --- End quote --- It is. See the graph 2N3055 posted. The manual of your LCR meter has similar graphs or at least a formula that can be used to derive such a graph. In the end an LCR meter is designed to measure components accurately but can only do so if there is a measurable voltage across the DUT. If you want to measure components over a wide frequency range, then a network analyser is a more suitable piece of equipment although the accuracy will be lower. For example: when doing Power Distribution Network measurements, you are measuring capacitors ranging from hundreds of pf to tens of uf and trace inductances (nano Henries) over a wide frequency range (up to several hundred MHz) in order to check the impedance of the power distribution network on a circuit board. |
| Martin72:
--- Quote --- The manual of your LCR meter has similar graphs or at least a formula that can be used to derive such a graph. --- End quote --- And it´s nearly always the same, I think because of the same measure principle. Here the diagram of the ET4410, where I must confess that I have problems to read it right - too many crosslines... ;) |
| 2N3055:
--- Quote from: Martin72 on July 09, 2023, 04:52:45 pm --- --- Quote --- The manual of your LCR meter has similar graphs or at least a formula that can be used to derive such a graph. --- End quote --- And it´s nearly always the same, I think because of the same measure principle. Here the diagram of the ET4410, where I must confess that I have problems to read it right - too many crosslines... ;) --- End quote --- Yes, nomograms like this really are better when colors are used.... But they exist as a handy reminder what exactly the numbers are on top of user intuition where limits are approximately. Basically, check what are limits of your LCR meter when measuring R. Those will be limits of measurement circuit. Then you know if test frequency is high, your L must not be higher impedance than what R you can measure. Or C cannot be smaller impedance then what R you can measure. On the same token, if frequency is too low for small L it will be represented by very small impedance, or small C will be very high impedance... Low frequency: good for large C and large L High frequency : good for small C and small L This nomogram is just nicely plotted that... |
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