Keithley 7077, Instruction Manual

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3
Applications
3-1
3.1 Introduction
General applications to test thick film resistor networks and
transistors are provided in this section. These applications
are intended to demonstrate the versatility of using the ma-
trix card in test systems.
3.2 Thick film resistor network testing
A dedicated matrix system for testing thick film resistor net-
works is shown in Figure 3-1. This system provides two dif-
ferent methods for checking thick films: four-wire resistance
measurement and voltage measurements using an applied
voltage. The Model 7077 used in this system is configured as
an 8
×
12 matrix.
The system shown in Figure 3-1 tests three 3-element thick
films, but can be expanded to test more using additional
Model 7077 matrix cards. The Model 707 Switching Matrix
will accommodate six matrix cards, allowing up to 18 three-
element thick films to be tested. Daisy-chaining five Model
707s expands the system to 30 matrix cards allowing 90
three-element thick films to be tested. The Model 708
Switching Matrix accommodates one Model 7077 Matrix
Card. Daisy-chaining five Model 708s expands the system to
five matrix cards allowing up to 15 thick films to be tested.
3.2.1 Four-terminal ohms measurements
For general purpose testing, the Keithley Model 2000 can be
used to make 4-terminal resistance measurements of each
thick film. As shown in Figure 3-2, Ohms HI and Ohms
Sense HI are connected to one matrix row, and Ohms LO and
Ohms Sense LO are connected to another matrix row. With
this configuration, the resistance of each resistor element
and/or combined elements can be measured by closing the
appropriate crosspoints. In Figure 3-2, crosspoints A1 and
B3 are closed to measure the combined resistance of R1 and
R2.
The effects of thermal EMFs generated by relay contacts and
connections can be canceled using the offset compensated
ohms feature of the Model 2000. To compensate for thermal
EMFs, close two crosspoints (such as A1 and B1). This will
short the input of the Model 2000, enabling zero to cancel in-
ternal offset, and then enabling offset compensated ohms.