SAM-III Construction Manual
See last page for document and copyright information, File: SAM-III Magnetometer Construction.doc, Page 32
The measured resistance should alternate between an open and short circuit. Note: Some digital
multimeters do not respond fast enough to provide a meaningful display, but the display should not
show a steady open (infinite resistance) or steady short (zero resistance). A low-inertia (small and light)
analog ohmmeter is best for this test but a digital multimeter can be used.
Press F1 if the test is successful and to move to the next test.
Test the Input
The input circuit is decoupled from the rest of the circuits by an opto-coupler (opto-isolator). An
external 12 V dc voltage source is required for this test. When F1 was pressed in the previous test, the
LCD should show
Digital input:
Apply voltage to
digital input.
Press F1 to abort.
The digital input test can be skipped by pressing F1. If you press F1, you should see
Digital input:
Test aborted
If the test is aborted, the SAM-III automatically will go to the next test.
To proceed with the test, refer to the X1 terminal block pinout shown above. Connect the + lead from an
isolated 12 Vdc power supply to pin 1 of X1 and the
–
lead to Pin 2. Note: 12 V dc is available between
pin 7 (+) and pin 8 (
–
) of X1. It may be used
to test the input but this voltage is not
isolated from the PCB ground, and it will not
be a true test of the isolated input circuit.
As soon as the SAM-III processor detects 12
V the following text will appear on the
display:
Digital input:
Test ok...
The SAM-III automatically will go to the next test.
Test and Adjust the Analog Output
The SAM-III has one analog output channel that provides a
voltage proportional to the K-Index computed by the SAM-III
sensor. The analog output is adjusted by potentiometers P1
and P2. The locations of P1 and P2 are shown below.
