Keithley 2700, Руководство пользователя, Страница: 90 / 500

Model 2700 Multimeter/Switch System User’s Manual Close/Open Switching Module Channels 2-35
The 2-wire functions include DCV, ACV, DCI, ACI,
Ω
2, CONT, FREQ, PERIOD, and
TEMP (thermocouple and thermistor). The 4-wire functions/operations include
Ω
4, TEMP
(4-wire RTD), RATIO, and CH AVG (ratio and channel average are covered in Section 5 ).
With a 4-wire function/operation selected, channels are paired as follows:
Schematic diagram
The simplified schematic diagram of the Model 7700 is shown in Figure 2-12 . Channels 1
through 20 are used for all measurements except amps. Channels 21 and 22 are used for
amps only.
There are two backplane relays (channels 24 and 25) to connect the input channel(s) to the
backplane of the Model 2700. With a 2-wire function (except amps) selected, channel 25
will close, and with a 4-wire function selected, both channels 24 and 25 will close.
There is a 2-pole/4-pole relay (channel 23) between channels 1-10 and channels 11-20.
When a 2-wire function (i.e., DCV) is selected, channel 23 opens (2-pole position) to
allow any of the 20 channels to be connected to the input backplane.
When a 4-wire function is selected, channel 23 closes (4-pole position) to isolate channels
1 through 10 from channels 11 through 20. With a system channel (1 through 10) closed,
its paired channel (11 through 20) will also close to connect the sense channel to the sense
backplane.
For the two current channels (21 and 22), signal HI and LO are routed directly to the
backplane when the channel is closed.
As shown in Figure 2-12 , there are also screw terminals labeled “Input,” “Sense,” and
“Amps.” The Input and Sense terminals are connected to the inputs of channels 24 and 25
(isolation relays). If channels 1 through 20 are not intended to be connected to the internal
DMM, channels 24 and 25 can be controlled independently using multiple channel
operation. The Amps terminals are connected directly to the DMM.
CH1 and CH11 CH6 and CH16
CH2 and CH12 CH7 and CH17
CH3 and CH13 CH8 and CH18
CH4 and CH14 CH9 and CH19
CH5 and CH15 CH10 and CH20