Dry circuit ohms measurement considerations
Dry circuit ohms uses a constant-current source with voltage monitoring that is used to clamp the
current source voltage. The current source remains constant as long as the monitoring voltage is less
than 20 mV. When the voltage exceeds 20 mV, the current source shunts current internal to the DMM
until 20 mV is maintained at the DUT.
When using dry circuit ohms, the DUT is shunted by 100 kΩ and 0.9 µF for the 1 Ω, 10 Ω, and
100 Ωranges. For the 1 kΩ and 10 kΩ ranges, it is shunted by 10 MΩ and 0.015 µF. This allows the
current source to have minimal overshoot voltage under transient conditions. When used with a
switching system, the overshoot is less than 40 mV in 20 µs.
Enable or disable dry circuit ohms from the front panel
Dry circuit ohms is an attribute set for the 4-wire ohm DMM function.
When the dry circuit ohms attribute is enabled, the offset-compensated ohms attribute is
automatically enabled (OC+ annunciator). If you do not wish to use offset-compensated ohms, after
setting dry circuit ohms, disable offset-compensated ohms using the information in Enable or disable
offset-compensated ohms (on page 4-67).
If the Series 3700A is being controlled remotely, press the EXIT key to place it in local mode.
To enable offset-compensated ohms, the Series 3700A DMM function must be set to four-wire ohms.
The Series 3700A is in 4-wire ohm mode when 4WΩ is displayed. Dry Circuit is active when the
DRY+ is displayed (see the following figure).
Figure 69: Enabling dry-circuit ohms
To enable/disable dry circuit ohms from the front panel:
1. Press the CONFIG key .
2. Press the DMM key .
3. Turn the navigation wheel to scroll to the "DRYCIRCUIT" menu item.
4. Press the navigation wheel to display ON/OFF settings for dry circuit ohms.
5. Select "ON" or "OFF" and press the navigation wheel again.
6. Press the EXIT key to leave the menu.
When enabled, the dry circuit ohms annunciator is on (DRY+).
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