National Instruments NI 4050 用户手册

© National Instruments Corporation

In the extended ohms range, the NI 4050 adds a 1 M

Ω 

resistor in parallel 

with the test resistor, and then calculates the value of the resistor being 
tested. The test current for the 200 

Ω

, 2.0 k

Ω

, and 20 k

Ω 

ranges is 100 µA. 

The test current for the 200 k

Ω

, 2 M

Ω

, and 200 M

Ω 

ranges is 1 µA.

Many traditional multimeters can take continuity measurements, which test 
for the presence or absence of continuity between the two test probes. 
These measurements are simply resistance measurements, where the 
resistance between the two probes is measured and compared to a set value. 
You can perform continuity measurements on a circuit by setting the 
NI 4050 to the 200 

Ω 

range and comparing the measured value to some low 

resistance value, typically 10 

Ω

. If the measured value is less than 10 

Ω

, 

there is continuity between the test probes.

To properly measure the forward voltage of a diode, make sure that the 
diode is not connected to any other circuits. The NI 4050 biases the diode 
with a current of 100 

µ

A and measures the resulting voltage drop, as 

illustrated in Figure 2-5. Diode measurements are made with a fixed range 
of 2.0 V.

Different multimeters use different currents to excite the diode. This may result in 

different readings for the same diode.

Figure 2-5.  Circuit for Diode Measurements

I

ex

V

sense

+

–

V

diode

V

sense

 = V

diode

+

–

I

ex

I

ex

HI

LO

Input

V

Ω