Extech 380193 comparison to BK Precision 886

[ScottA]

A buddy of mine at work has a BK Precision 886 LCR meter, I recently discovered, so I borrowed it and did a correlation with my Extech 380193.

The BK is a higher end (at least price-wise) model. It does measure more frequencies (100, 120, 1000, 10000, 100000 Hz) and also provides impedance and phase angle measurements.

Most measurements correlate to within a fraction of a percent across a wide range of values.

I hope this also serves to clarify some of the measurements that the Extech outputs, since the documentation on that meter is so thin.

Based on this study, I conclude that the "R" in the primary (L,C,R) functions of the Extech is the equivalent series resistance (ESR). The secondary R that the Extech provides is ESR and EPR (equivalent parallel resistance) in the series and parallel modes, respectively. The difference between the primary ESR and secondary ESR is unclear. The measurements correlate well, although the primary value is consistently lower by a hundred or so Ohms at 1000 Hz (at 120 Hz, they are much closer and the primary value may be higher or lower). As far as I can tell, the primary mode seems to be done with an internal calibration, as the measurement tends to start at the higher value (close to the secondary value) and settle in at the lower value after it chews on it for a few seconds. The primary mode also tends to continuously recalculate, whereas the secondary mode does not. I assume this means that the primary mode is more accurate.

Also, the ESR at 120 Hz correlates well with the DCR measured by the BK, so for all practical purposes, the R at 120 Hz measured by the Extech can be treated as the DCR for pickups. Some of the correlations are shown below. The grey dotted line represents y=x. The correlation for the ESR is the least robust, but still not bad. It should be noted that the Extech actually seems to handle ESR measurement better than the BK. The BK in fact cannot handle pickup ESRs greater than about 9500 Ohms. That's why that comparison is truncated. The Extech seems to handle ESR (assuming that is what this measurement actually is) across the board.

I measured a representative range of my models spanning a wide range of L and R and with varying degrees of eddy current loading.

I hope you find this useful. I'm certainly very comfortable with the Extech numbers at this point. The inductance values are spot on at both 120 and 1000 Hz.

[kayakerca]

Also, the ESR at 120 Hz correlates well with the DCR measured by the BK, so for all practical purposes, the R at 120 Hz measured by the Extech can be treated as the DCR for pickups.

I have an Extech LCR200 which, unlike the Extech 380193, does natively measure DCR. I just went down to the shop, hooked up a pickup and did a quick test to confirm your findings Scott. My LCR200 when set to 120 Hz produces an Rs = 5.936 kΩ. I toggled over and it showed a DCR = 5.941 kΩ.

Pretty close I'd say.

[Mike Sulzer]

Yes, your result concerning the equivalence of the series resistance at 120 Hz in the inductance measurement to the DCR confirms what I have measured and discussed before. This result shows that the eddy current losses are small at 120H. It also shows that the inductance measurement at 120 Hz is the coil inductance, to the limit of its accuracy, and so in cases where the 120 Hz and 1 KHz inductances differ significantly, the 120 Hz is the one that best describes the primary inductance in a circuit model of the pickup. And you have confirmed that the Extech and the more expensive meter track very well in the 120 Hz inductance measurement.

A buddy of mine at work has a BK Precision 886 LCR meter, I recently discovered, so I borrowed it and did a correlation with my Extech 380193.

The BK is a higher end (at least price-wise) model. It does measure more frequencies (100, 120, 1000, 10000, 100000 Hz) and also provides impedance and phase angle measurements.

Most measurements correlate to within a fraction of a percent across a wide range of values.

I hope this also serves to clarify some of the measurements that the Extech outputs, since the documentation on that meter is so thin.

Based on this study, I conclude that the "R" in the primary (L,C,R) functions of the Extech is the equivalent series resistance (ESR). The secondary R that the Extech provides is ESR and EPR (equivalent parallel resistance) in the series and parallel modes, respectively. The difference between the primary ESR and secondary ESR is unclear. The measurements correlate well, although the primary value is consistently lower by a hundred or so Hz. As far as I can tell, the primary mode seems to be done with an internal calibration, as the measurement tends to start at the higher value (close to the secondary value) and settle in at the lower value after it chews on it for a few seconds. The primary mode also tends to continuously recalculate, whereas the secondary mode does not. I assume this means that the primary mode is more accurate.

Also, the ESR at 120 Hz correlates well with the DCR measured by the BK, so for all practical purposes, the R at 120 Hz measured by the Extech can be treated as the DCR for pickups. Some of the correlations are shown below. The grey dotted line represents y=x. The correlation for the ESR is the least robust, but still not bad. It should be noted that the Extech actually seems to handle ESR measurement better than the BK. The BK in fact cannot handle pickup ESRs greater than about 9500 Ohms. That's why that comparison is truncated. The Extech seems to handle ESR (assuming that is what this measurement actually is) across the board.

I measured a representative range of my models spanning a wide range of L and R and with varying degrees of eddy current loading.

I hope you find this useful. I'm certainly very comfortable with the Extech numbers at this point. The inductance values are spot on at both 120 and 1000 Hz.

[ATTACH=CONFIG]25634[/ATTACH]

[Joe Gwinn]

The historic problem with handheld LCR meters (except the Extech) was that they did not handle low-Q inductors properly, committing gross errors.

While I don't have a B+K 886 to play with, I can suggest how to test it: Put an few-henry audio choke in series with a 50,000 ohm pot, and see how well the two instruments' readings compare as the pot is turned.

By the way, measurements of pickups at 10,000 Hz and 100,000 Hz are likely to be confusing, as the usual self-resonant frequency is at or below 10,000 Hz. When measured above resonance, the inductance is swamped by the parallel capacitance, and is the meter is set to inductance, the results will be more entertaining than informative.

[ScottA]

The historic problem with handheld LCR meters (except the Extech) was that they did not handle low-Q inductors properly, committing gross errors.

While I don't have a B+K 886 to play with, I can suggest how to test it: Put an few-henry audio choke in series with a 50,000 ohm pot, and see how well the two instruments' readings compare as the pot is turned.

By the way, measurements of pickups at 10,000 Hz and 100,000 Hz are likely to be confusing, as the usual self-resonant frequency is at or below 10,000 Hz. When measured above resonance, the inductance is swamped by the parallel capacitance, and is the meter is set to inductance, the results will be more entertaining than informative.

The high frequency measurements of pickups are quite flaky on the BK, although they are fairly consistently flaky in that the same models set up in about the same place and there are clear differences between models.

I get my resonance information using the network analyzer function of the Syscomp.

The high frequency measurements on the BK do show sensitivity to factors driving capacitance. For example there is a clear difference at 10 and 100 k Hz between the same pickup with two conductor wiring and a shielded 4-conductor cable, whereas they are difficult to differentiate with LCR measurements at 1000 Hz (refer to my earlier thread about the capacitive losses with 4-conductor cables). Also the capacitance measurements at 100 k look pretty reasonable for the most part, although there is some variability in these as well.