Keithley 2182A/E Digital-Multimeter, DMM, 2182A/E Datenbogen

Produktcode

2182A/E

W L

L M

E & S

www.keithley.com

1.888.KEITHLEY

(U.S. only)

A Greater Measure of Confidence

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optional accessory: Model 2187-4 low Thermal

Test lead Kit

The standard cabling provided with the Model

2182A Nano volt meter and Model 622X Current

Sources provides everything normally needed

to connect the instruments to each other and to

the DUT . The Model 2187-4 Low Thermal Test

Lead Kit is required when the cabling provided

may not be sufficient for specific applications,

such as when the DUT has special connection

requirements . The kit includes an input cable

with banana terminations, banana extensions,

sprung-hook clips, alligator clips, needle probes,

and spade lugs to accommodate virtually any

DUT . The Model 2187-4 is also helpful when the

DUT has roughly 1G

W impedance or higher .

In this case, measuring with the Model 2182A

directly across the DUT will lead to loading

errors . The Model 2187-4 Low Thermal Test Lead Kit provides a banana cable and banana jack

extender to allow the Model 2182A to connect easily to the Model 622X’s low impedance guard

output, so the Model 2182A can measure the DUT voltage indirectly . This same configuration also

removes the Model 2182A’s input capacitance from the DUT, so it improves device response time,

which may be critical for pulsed measurements .

Three Ways to Measure Nanovolts
DC nanovoltmeters. DC nanovoltmeters

and sensitive DMMs both provide low noise

DC voltage measurements by using long

integration times and highly filtered readings

to minimize the bandwidth near DC .

Unfortunately, this approach has limitations,

particularly the fact that thermal voltages

develop in the sample and connections vary,

so long integration times don’t improve

measurement precision . With a noise

specification of just 6nV p-p, the Model 2182A

is the lowest noise digital nanovolt meter

available .

AC technique. The limitations of the long

integration and filtered readings technique

have led many people to use an AC technique

for measuring low resistances and voltages .

In this method, an AC excitation is applied

to the sample and the voltage is detected

syn chronously at the same frequency and

an optimum phase . While this technique

removes the varying DC component, in many

experiments at high frequencies, users can

experience problems related to phase shifts

caused by spurious capacitance or the L/R

time constant . At low frequencies, as the

AC frequency is reduced to minimize phase

shifts, amplifier noise increases .

The current reversal method. The Model

2182A is optimized for the current reversal

method, which combines the advantages of

both earlier approaches . In this technique,

the DC test current is reversed, then the

difference in voltage due to the difference

in current is determined . Typically, this

measure ment is performed at a few hertz (a

frequency just high enough for the current

to be reversed before the thermal voltages

can change) . The Model 2182A’s low noise

performance at measurement times of a

few hundred milliseconds to a few seconds

means that the reversal period can be set

quite small in comparison with the thermal

time constant of the sample and the con-

nections, effectively reducing the impact of

thermal voltages .

180

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190

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200

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220

17 25 33 42 50 58 67 75 83 92 100 108 117 125

Voltage

(nV)

Temperature

(

°C)

Minutes

–10

–5

figure 5. The Model 2182a’s delta mode provides extremely stable results, even in the pres-

ence of large ambient temperature changes. In this challenging example, the 200nV signal

results from a 20µa current sourced by a Model 6221 through a 10m

W test resistor.

2182a

Nanovoltmeter

figure 7. Model 2182a rear panel

figure 6. Model 2187-4 Test lead Kit