Specifications

Although this technique can provide the best accuracy, especially for low impedance measurement,

the extension length is limited by the measurement frequency. This is because the total length of the

series cables must be sufficiently shorter than the wavelength of the measurement signal. The fol-

lowing equation gives a guideline for determining typical cable length limitation:

F (MHz) x L (m) ≤ 15 F: Measurement frequency (MHz)

L: Cable length (m)

When the cable length is one meter, the maximum frequency limit will be approximately 15 MHz. If

the cable length or frequency exceeds this limit, the auto-balancing bridge may not balance. For

higher frequency measurements or longer extension, the shielded 2T extension technique, which is

described next, should be used.

Note: The 4294A helps prevent the cable length limitation by terminating the test ports with the

same impedance as the characteristic impedance of specified test cables at high frequencies.

However, the practical cable length limit due to increase in measurement error still exists.

Note: Additional measurement error and the compensation regarding the 4TP-4TP extension are

described in Section 4.5.

Figure 3-12. 4TP-4TP extension

(a) Schematic diagram

DUT

LCR meter

Test cables

(16048A etc.)

Extended cables

LCR meter

(b) Connection image

BNC (f ) – BNC (f ) adapters

(Part number: 1250-0080)

Plate for holding the adapters

BNC cables

Test cables

Connect here

3-12