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3 - Installation
34
Refer to the previous discussion under "Remote Sense Connections" and "Local Sensing" for more
information about remote and local sensing. Standard dc source units are shipped from the factory with
the output compensation set to HRemote mode. This mode provides the fastest output response but
requires an external capacitor for stable operation.
To program the compensation mode from the front panel, press the
Output key, use ' to scroll to the
COMP command, press &
&&
& to select one of the four compensation mode settings, and then press Enter.
To have the unit turn on with a different output compensation setting, save this state in location 0 and set
the power-on state to RCL 0. The following table summarizes the four programmable compensation
modes.
Mode
Description
LLocal
1
Used for slower response with short load leads or bench operation. This produces the
slowest output response, but provides the best stability (no external capacitor needed).
LRemote
Used for slower response with long load leads using remote sensing.
HLocal
Use for faster response with short load leads or bench operation (no external cap needed).
HRemote
2
Used for faster response with long load leads using remote sensing. This produces the
fastest output response, but requires an external capacitor for stable operation.
1
Corresponds to Low mode on earlier models (66311B/D, 66309B/D).
2
Corresponds to High mode on earlier models (66311B/D, 66309B/D).
If you do not know the input capacitance of the phone that you are testing, leave the input capacitance set
to LLocal mode initially. This is because in LLocal mode, the output of the dc source will be stable when
testing cellular phones that have virtually any input capacitance (from 0 µF to 12,000 µF). LLocal mode
however, has the slowest transient response (see appendix A).
The HRemote mode output compensation setting provides the fastest transient response performance for
phones with input capacitances greater than 5µF. Most phones have input capacitances greater than 5 µF.
However, the operation of the dc source may be momentarily unstable with phones that have input
capacitances less than 5 µF, or if the output sense leads are not connected and you are operating in
HRemote mode.
Use the output sense detect circuit to first determine that the sense and load leads are properly connected
to the device under test. Then, if you are testing phones in HRemote mode and want to determine if the
input capacitance of your phone is less than 5 µF, perform the following test.
NOTE: It is important that this test is done with the dc source installed in the test system where it
will be used, since system stability is also dependent on wiring and the phone impedance.
1. Connect the phone to the dc source and place it in standby mode.
2. Check the last two digits of the voltage reading on the front panel of the dc source.
3. If the last two digits are fluctuating, it is an indication that the phone capacitance may be less than
5 µF and the dc source is unstable.
4. Place the output compensation of the dc source in LLocal mode.
5. If the last two digits of the voltage reading are now stable, your phone most likely has an input
capacitance less than 5 µF.