Operator`s manual

41 Signametrics
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process. This will speed up the acquisition time when condition change.
Selecting the appropriate external resistor is very important. It sets the accuracy and range of the synthesized va
Functions associated with the synthesis of resistance include DMMSetExternalShunt(), which sets the value of the
external shunt, and DMMSetResistance(), which control the value to be synthesized. The external resistor should
be 100Ω to 10MΩ. Set the measurement to 10 or higher. 20rps is optimal. The Closed loop flag does not have an
effect on this function. Reselecting the function, or resetting the value has the effect of restarting the synthes
Figure 4-16. Synthesizing resistance into a voltage divider circuit.
4.15 Interfacing to the SM4040 series Relay Scanners
The SM2040 series of Digital Multimeters are designed to interface to the SM4000 series relay scanners. The
following section describes both, the hardware interface and the software functions required to implement a
synchronized operation.
4.15.1 Triggering the SM2040 DMMs
The SM2040 series can accept a hardware trigger from many sources, including the SM4000 scanners. The latter
can be setup to trigger a measurement any time the scanner selects a new channel. The interface requires a single
jumper between the SM4000 Trig_com and Common lines, and a connection between the SM4000 +5V and
TRIG_out to the SM2040 Trigger inputs. The various SM4000 auto-scanning operations can run independently
from the computer, whereby the Scanner selects channels from its Scan List table, and the DMM is triggered to take
measurements following each channel selection.
Figure 4-16. Trigger interfacing connection to an SM2040 class of DMMs.