National Instruments NI 4050 用户手册

These additional errors are shown in Appendix A, 

. While the 

NI 4050 is characterized and specified over the 20 Hz to 25 kHz frequency 
range, measurements outside of this range can still be made with decreased 
accuracy.

The NI 4050 measures 2-wire resistance by passing a current through the 
device under test and reading the resulting voltage drop through the same 
connections, as illustrated in Figure 2-4. The resistance value is then 
computed using Ohm’s Law (R=V/I). To accurately measure the value of 
a resistor, make sure the resistor is not connected to any other circuits. 
Erroneous or misleading readings can result if the resistor you are 
measuring is connected to external circuits that supply voltages or currents, 
or to external circuits that change the effective resistance of that resistor.

Figure 2-4.  Circuit for 2-Wire Resistance Measurements

The NI 4050 has five basic input ranges for 2-wire resistance as well as an 
extended range. The basic ranges are 200 

Ω

, 2.0 k

Ω

, 20 k

Ω

, 200 k

Ω

, and 

2   M

Ω

. With the extended range, measurements up to at least 200 M

Ω 

are 

possible.

 R

unknown

+

–

V

sense

I

ex

I

ex

I

ex

 R

unknown 

=

 

V

sense

I

ex

I

ex 

= 100 

µ

A (200 

Ω

, 2 k

Ω

, 20 k

Ω

 ranges)

1 

µ

A (200 k

Ω

, 2 M

Ω

, 200 M

Ω

 ranges)

HI

LO

Input

V

Ω