User`s guide

Programming the DC Source - 7

Making Measurements

The Agilent 66111A and the Agilent 66311B both have excellent output voltage and current

measurement capability. The Agilent 66311B Mobile Communications Dc Source also has the ability to

make several types of voltage or current measurements. These expanded measurement capabilities are

particularly useful for loads that draw current in pulses.

NOTE: Because there is only one measurement buffer, you cannot measure output voltage and

current simultaneously.

All measurements are performed by digitizing the instantaneous output voltage or current for a defined

number of samples and sample interval, storing the results in a buffer, and then calculating the measured

result. Many parameters of the measurement are programmable. These include the number of samples,

the time interval between samples, and the method of triggering. Note that there is a tradeoff between

these parameters and the speed, accuracy, and stability of the measurement in the presence of noise.

There are two ways to make measurements:

♦

Use the MEASure commands to immediately start acquiring new voltage or current data, and return

measurement calculations from this data as soon as the buffer is full. This is the easiest way to make

measurements, since it requires no explicit trigger programming.

♦

Use an acquisition trigger to acquire the data as discussed under “Triggering Measurements”. Then

use the FETCh commands to return calculations from the data that was retrieved by the acquisition

trigger. This method gives you the flexibility to synchronize the data acquisition with a transition in

the output voltage or current. FETCh commands do not trigger the acquisition of new measurement

data, but they can be used to return many different calculations from the data that was retrieved by

the acquisition trigger. Note that if you take a voltage measurement, you can fetch only voltage data.

NOTE: For each MEASure query, there exists a corresponding FETCh query. FETCh queries

perform the same calculation as MEASure queries, but do not acquire new data.

Controlling Measurement Samples

You can vary both the number of data points in a measurement sample, as well as the time between

samples. This is illustrated in Figure 7-2.

SENS:SWE:POIN

# of points>

SENS:SWE:TINT

time

Figure 7-2. Commands that Control Measurement Time