Review: Mastech MS5308 LCR Tester

[Stephan_T]

Hi Martin,

Looking at the manual which I found at

http://www.aidetek.com/New_products_info/Datasheet/huayi/MS5308_english_manual.pdf

the ranges do not only tell us about resolution and accuracy. We may also notice, that many of the capacities you tested are far out of the described ranges.

4000uF, 100uF seems to fit only the lower scales.

Highest Capacity Ranges at different frequencies:

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Frequency Capacity Res.  Accuracy
100Hz/120 20.00mF 0.1mF  2.0%+5d  # This is within spec
1kHz     2000.0uF 0.1uF  1.0%+5d  # Already out with 4000uF but ok for 95uF
10kHz    2000.0nF 0.1nF  2.0%+5d  # Far over the limit
100kHz   200.00nF 0.01nF 5.0%+5d  # Way beyond

Let's take a look at the expected values of the reactance for the desired capacities and frequencies:

X(C,f) = 1/(2*pi*C*f)

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C f X
95uF 100Hz 16.75 Ohm  # OK
95uF 1kHz 1.68  Ohm  # still good
95uF 10kHz 0.17  Ohm  # a little low
95uF 100kHz  0.02  Ohm  # getting tiny
@min 26:00 The issue is that you are 100 times beyond the spec.
Testing 95uF at 100kHz does not makes any sense to me.

@min 28:36
Wow, now you go even further!

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C f X
4.3mF 100Hz 0.37  Ohm
4.3mF 1kHz 37   mOhm
4.3mF 10kHz 3.7  mOhm
4.3mF 100kHz 0.37 mOhm

Even the pure resistance test at 100kHz has only a resolution of 1mOhm:

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100kHz  20.000Ohm  0.001 Ohm  1.0%+5d
0.4 mOhm is way beyond what makes sense to measure.

100Hz is in spec, but every thing above is just good will.

There are not enough "pokie out tongues" to express the relation of imaginary 0.37 mOhm to the real world of electronics

@min 31:00
1uF is also not such a small capacitor. It is out of spec at the 100kHz frequency.

@min 32:00
10uF? Seriously? You should go down instead of up with the capacity if you would like to make sense at higher frequencies.

@min 33:45 "high losses in a 10uF at 10kHz" Who cares? Dissipation and quality factors matter for oscillators, which use much smaller capacities to achieve high frequencies.
 
@min 34:23 "heavens"
@min 34:40 "that shows 44, which is really high" no it is not, it is nF not uF, but at 100kHz this is all just house numbers.
"2.48 which is really low", no  2.48uF= 2480nF. You are confused. I sometimes need mind overload protection, when viewing your videos

@min 35:00: it is again way beyond the spec, which ended at 2uF / 10kHz.
Measurement at 1kHz would be OK, but not at 100kHz.

@min 37:
Phase angle is an interesting option. You may try this with your high capacity high frequency mysteries. There, the phase angle should dramatically drop to show you, how far you get away from the ideal (-90°) capacitor.

4.74 Ohms ESR and

C = 2.48uF @ f= 100kHz

makes X(C,f) = 1/(2*pi*f*C) = 0.641 Ohm pretty low compared to the ESR!

atan(Xc/ESR)= 7,71° Getting far beyond the cutoff frequency (phase angle 45°) even with the ESR makes no sense to me.

@min 39:30 ESR and capacity are probably not measured at the same frequency. A large capacity at high frequency shortens the AC current and drops the AC reactance (Xc) very low, which is fine to measure the ESR. But it is no good to measure capacity.

Regards,
Stephan

PS.: Before making the tutorial about capacitors, you may dig a little deeper into the theory of them. Take a look at Jeri Ellsworth's Vimeo Video about capacitors. But don't kill any birds with them

By the way, your analogy to balloons and bladders is opening Pandora's box in term of your hydraulic example. Once you open the tubes with monopoles  where there should be only dipoles, the electric sauce may flow out uncontrollable The capacitor should be seen like all other elements as having at least two pipes connected to the circuit. You can regard the capacitor as a vessel with an elastic membrane in it.

[MJLorton]

Thanks....and thank heavens...I still have a lot to learn!

[Stephan_T]

Hi Martin,

(about your comment @ 10:27 "T4D #49 - Feedback, news and AC to DC power supply")
I guess that you mean the Bode plots as the  graphical display of the response of a capacitor over the frequency range".

Actually it not a matter of the capacitor alone, but the behavior (gain value) of RC circuits which this is about. The combination of a capacitor and a resistor act together as a filter, and according to the way you set the circuit up, you can differ between a high or a low pass filter.

Seeing the glow in your eyes, about a new gadget on the horizon ("a very top end meter") I actually had to laugh What wold you say if i tell you, that you already have all the equipment it takes, to generate exactly these kind of diagrams? Seeing Dave Jones' video (EEVblog #396 - Bode Plotting on Your Oscilloscope) explaining how it is done, reminded me, that I have done the very same thing more than 30 years ago in school. At that time, all the equipment was analog, but the method back then was exactly like Dave describes it.

What it takes is the function generator with the sweep feature and the oscilloscope.

BTW. I'm currently playing around with gnuplot. It makes it easy to visualize the mathematical background of the things we are dealing with. E. g. the exponential functions for charging and discharging capacitors and the famous time constant are shown here:





At the end of this post, you find the source code to create the diagrams. Gnuplot is free software and available for many platforms. A nice feature of gnuplot is, that you can also plot data very easy together with functions. It is perfect to visualize data created by arduino.

Regards,
Stephan

PS. Attached is also a plot of the curve that Dave is exploring. I choose the same resistor value and displayed a couple of plots for different other capacities. The red line is his example of 2.2nF.

Finally I also attached a plot to visualize the frequency dependent values for a large variety of capacitors  (10pF, 100pF, 1nF, 10nF, 100nF, 1uF, 10uF, 100uF, 1000uF) . You may meditate a little bit about what it means, when we are entering the micro ohms range

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set  terminal wxt enhance # enable subscript and greek letters


set title "Discharging a Capacitor with {/Symbol t}=20s" # {/Symbol g } =tau
set ylabel "U(t) in V"
set xlabel "t in s"

u0  =  5.000
tau = 20
discharge(t) = u0 * (t<0 ? 1 : exp(-t/tau))

set xrange [-10:150]
set yrange [0:u0+1]


set arrow from 5*tau,1 to 5*tau, 0 lt rgb "#0000FF"
set arrow from 0,1 to 0, 0 lt rgb "#dd00FF"

n=0
set arrow from n*tau,discharge(n*tau) to (n+1)*tau,0  lt rgb "#00aa00"
n=1
set arrow from n*tau,discharge(n*tau) to (n+1)*tau,0  lt rgb "#00aa00"
n=2
set arrow from n*tau,discharge(n*tau) to (n+1)*tau,0  lt rgb "#00aa00"
n=3
set arrow from n*tau,discharge(n*tau) to (n+1)*tau,0  lt rgb "#00aa00"

plot discharge(x) linewidth 2 title "U_0 * e^{-t/tau}"

######################################

unset arrow

set title "Charging a Capacitor with {/Symbol t}=20s" # {/Symbol t} = tau
set ylabel "U(t) in V"
set xlabel "t in s"

u0  = 5.000
tau = 20
charge(t) = u0 * (t<0 ? 0 :  (1 - exp(-t/tau)))

set xrange [-10:150]
set yrange [0:u0+1]

set arrow from 0,u0 to 160, u0 lt rgb "#0000FF"
set arrow from 5*tau,u0-1 to 5*tau, u0 lt rgb "#0000FF"
set arrow from 0,u0-1 to 0, u0 lt rgb "#dd00FF"

n=0
set arrow from n*tau,charge(n*tau) to (n+1)*tau,u0  lt rgb "#00aa00"
n=1
set arrow from n*tau,charge(n*tau) to (n+1)*tau,u0  lt rgb "#00aa00"
n=2
set arrow from n*tau,charge(n*tau) to (n+1)*tau,u0  lt rgb "#00aa00"
n=3
set arrow from n*tau,charge(n*tau) to (n+1)*tau,u0  lt rgb "#00aa00"

plot charge(x) linewidth 2 title "U_0 * (1 - e^{-t/tau})"


[MJLorton]

Brilliant, thanks for the input! After the glint in my eye and then seeing the price....I did some searching on measuring both capacitors and inductors with a scope and function generator so something to try soon.