NF ZM2376 - AC Impedance Measurement Accuracy

6.6 Performance Testing
6-8 ZM2376
6.6.5 AC Impedance Measurement Accuracy
Described here is the easy checking method. For the correct test, request NF Corporation to make
test.
Standard: To make correct test, prepare a 4-terminal-pair standard with approximately 1/3 or
less in calibration accuracy against the accuracy of ZM2376. Described here is an
example of test where easy-to-available standard is used.
When the frequency is low (for example, 120Hz), you can use a resistor whose
calibration value of impedance is not provided at each frequency for a simple test,
by considering its impedance equal to the DC resistance. For the range of 10 to
100k having good frequency response, you can obtain the impedance at 100kHz or
less for a simple test in the following procedure.
• Calibration value Rdc of DC resistance
• From the equivalent series inductance Ls[H] at 1MHz or the equivalent parallel
capacitance Cp[F] , calculate the complex impedance Z
．
by:
Z
．
= Rdc + j ω Ls or Z
．
= 1/(1/Rdc + j (ω Cp))
|Z
．
| = √( Rdc
2
+ (ω Ls)
2
) or |Z
．
| = Rdc/√( Rdc
2
(ω Cp)
2
+ 1)
θ = tan
-1
(ω Ls / Rdc) or θ = - tan
-1
(ω Cp Rdc)
where angular frequency ω = 2πf, f is frequency[Hz]
When a calibrated general resistor is connected via test fixture to be used as the
standard, the test should be only intended for quick operation check, since
additional errors occur due to the test fixture or due to surrounding environment
differences from the calibration.
Connection: Connect the standard to the measurement terminal of ZM2376.
Setting: After initializing the setting, setting as shown below.
Measurement frequency = 120Hz, 1kHz, 10kHz, 100kHz, 1MHz, 5MHz
Measurement signal level = 1V (initial value)
Measurement speed = SLOW, Averaging count = 1 (initial value)
Cable length correction = 0m (initial value)
Measurement range = Fix it to the specified range.
Auto selection may not allow the specified measurement range. Accordingly, be
sure to fix it to the specified measurement range.
Measurement: First, measures the OPEN correction and SHORT correction.
Thereafter, measure the standard according to the contents in table shown below.
Evaluation: If the measurement values are within the range stated below, it is approximately
correct.
Calibration value of standard ± (Calibration accuracy of standard + Accuracy
specification of ZM2376)