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5.5 Hall Generator
5.5.1 User
Programmable Cable
5.5.2 Ohms
Measurement Mode
The Model 425 will operate with a discrete Hall generator when a suitable probe is
not available. You can program nominal sensitivity and serial number into a blank
connector (HMCBL-XX, ordered separately) to provide all gaussmeter functions
except field compensation. If the HMCBL cable is not loaded with sensitivity informa-
tion (or a 0.0 sensitivity is mistakenly entered), the Model 425 reverts to resistance
measurement.
Unlike a fully calibrated probe, the accuracy is affected by the Hall sensor non-linearity.
If you connect an HMCBL cable with no sensitivity information (a new blank cable) to
the Model 425, a message stating "invalid probe" displays. Press Enter to clear the
message. Then program the cable with the serial number and nominal sensitivity of
the Hall generator.
If you need to change a previously programmed HMCBL cable, connect the HMCBL
cable to the instrument. If an invalid HMCBL cable is attached (for instance, a fully
calibrated Lake Shore cable), and the HMCBL program is attempted, a message stat-
ing "Invalid MCBL Cable" will appear for approximately 5 s
the cable is properly connected. If the invalid message continues to appear, either
replace the cable with a proper HMCBL cable or contact Lake Shore Service.
Enter the nominal sensitivity in mV/kG. This sensitivity is based on a 100 mA Hall cur-
rent. Use these ranges to set the nominal sensitivity value:
D Between 0.550 mV/kG and 1.100 mV/kG (HST)
D Between 5.500 mV/kG and 11.000 mV/kG (HSE)
D Between 550 mV/kG and 1100 mV/kG (gamma)
The Model 425 will adjust the available ranges based on the values entered for the
current and sensitivity.
Using a sensitivity outside the above ranges may cause reduced performance. Values
near, but lower than the "55" minimum will reduce resolution. Values near, but above the
"11" maximum may cause an instrument overload (OL) condition before full scale range is
reached. Therefore, using Hall generators with sensitivities outside the above-indicated
ranges is discouraged.
All of the above entries will be stored in the HMCBL cable PROM (located in the con-
nector). Thus, any time you use the cable/Hall generator combination, the Model 425
will recognize the stored parameters, and operation may proceed. You can reprogram
the HMCBL cables for other Hall generators as needed.
You can connect a Hall generator directly to the Model 425 without using an HMCBL
cable. Probe parameters can be configured as stated above, but the settings will be
lost if power is cycled.
Menu navigation:
Probe Setup (press and hold for 3 s)Q HMCBL Qserial number entryQ
nominal sensitivity entry
Interface command: PRBSENS? (query only)
The Model 425 can make a 4-lead resistive measurement. If the sensitivity of the
probe is set to 0, the instrument will read in ohms. Instrument features are limited in
this mode. The following ranges are available in this mode: 3.5 m), 35 m) , 350 m) ,
and 3.5 ).
5.5 Hall Generator
43
.
If this occurs, verify that
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