The peak will only show the ESR and that can in some rare cases (got some samples here) still be good. An impedance meter shows you there is "some" problem. That is why 100 Hz and 1 KHz will stay standards for measuring C But if capacitance is dropped a lot, Z will be higher. But you can not measure C with 100 kHz because the appearant capacitance there differs a lot from the true capacitance.
So that is why it is more convinient to measure at higher frequency. A very good 1 nF cap with a low D of 0.001 has an ESR at 1 kHz of 159 Ohm. My home made ESR meter measures down to 100 nF and even lower. reactance = 1/(2pifC) and ESR = D x reactance Because at 100kHz the jX of Z is neglectible for large enough caps, ESR will be the main part of Z. Z = impedance = (R -jX) or ( ESR and reactance). Most manufactures state |Z| at 100kHz and ESR as a function of D at 1 kHz or 100/120 Hz. Capital letters used in the subscript indicate that hFE refers to a direct current circuit.
'E' refers to the transistor operating in a common emitter (CE) configuration. 'F' is from forward current amplification also called the current gain. From the wiki: Etymology of hFE The 'h' refers to its being an h-parameter, a set of parameters named for their origin in a hybrid equivalent circuit model. But these are exeptions, just to tell you, never trust any instrument without thinking or cross checking. The Tek curvetracer showed me the real problem. The Peak and some transistor testers told me it was good. I have seen transistors with a perfect gain at a steady Ib, but an increase of Ib did not give a single reaction. But Datasheets show it so it is just a test. At DC the amplification can be 100 but at some frequeny, called Ft, the gain is dropped to 1 so if your peak shows you a gain of 100, this will not say this transistor has still a gain of 100 in your application at 10 MHz. The other one is the result of delta Ic to delta Ib, sometimes called small signal amplification. The first is the DC amplification of a common emitter amplifier (F=forward, E= common emitter, capitals is DC ) and I think this is what the peak measures. Just for the record, it is h FE and h fe, just two of the many " h" or hybrid parameters that excist.
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