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Section 13: Model 3750 multifunction control card
Series 3700A Switch and Control Cards Reference Manual
13-14
3700AS-909-01 Rev. B / December 2011
The connector labeled P3 contains all of the jumpers needed to configure digital I/O and VEXT1,
VEXT2. The connector labeled J5 contains a single jumper option that configures the backplane
relays. See the following table for individual jumper locations and effects.
Desired effect
P3 pin numbers
Install all 8 pull-up resistors on CH1
Jumper 1 - 2
Install all 8 pull-up resistors on CH2
Jumper 3 - 4
Install all 8 pull-up resistors on CH3
Jumper 7 - 8
Install all 8 pull-up resistors on CH4
Jumper 5 - 6
Install all 8 pull-up resistors on CH5
Jumper 9 - 10
CH1, CH2, CH4 connect pull-up voltage to +5 V
Jumper 11 - 13
CH1, CH2, CH4 connect pull-up voltage to VEXT1
Jumper 13 - 15
CH3, CH5 connect pull-up voltage to +5 V
Jumper 12 - 14
CH3, CH5 connect pull-up voltage to VEXT2
Jumper 14 - 16
Connect VEXT1 to VEXT2
Jumper 17 - 18
For backplane configuration at J5, jumper pins 2-3 to allow the Model 3750 to make backplane
connections during calibration with a system DMM. If you do not want to ever physically allow the
Model 3750 to make backplane connections, jumper pins 1-2. By populating this jumper in this way,
an additional amount of safety is provided to a system that may have high voltage connections made
to the backplane.
Calibration
To maintain specified performance over time, the analog output channels and the counter channels
might need to be calibrated. The Model 3750 supports automatic in-system calibration if a DMM is
present. Otherwise, an external DMM of 6.5 digits of accuracy or better can be used.
NOTE
When performing a user calibration, final accuracy is determined by the standards used. Always
verify the calibration results with a calibrated instrument capable of making measurements that
exceed the specifications of the Model 3750.
We recommend that the Model 3750 is calibrated in the end application whenever possible so that
the thermal and electrical operating environments can be accounted for. Best results will be obtained
whenever this can be done and up to 8x improvements in offsets are typical.
Preparing for calibration
Before performing the calibration steps, be sure that the Model 3750 is properly disconnected from all
external circuits. If an in-system DMM is to be used, disconnect the external ABUS from other
mainframes and instruments that might be connected. If possible, disconnect all Model 3750 cables
as well. Excessive capacitance on the counter channels can cause that part of calibration to fail. If a
Model 3750-ST accessory is used, you can keep this connected as long as external circuits are
disconnected.
Prior to calibration, the channel must be unlocked for calibration.
channel.calibration.unlock(<ch_list>, <password>)
The actual calibration is performed in several steps. In each step, the hardware outputs a value and
expects a measured value to be entered. Once all the steps are complete, the Model 3750 calculates
new calibration constants to be used until the next calibration takes place.
The following topics describe a list of steps to be performed to calibrate the Model 3750.