14
RESISTANCE ADJUSTMENTS
1.
Select 2
nd
range.
2.
Connect a standard resistor ½ scale of the selected range.
Example: If the 200Ω range is selected connect to a 100Ω standard resistor.
3.
Adjust R15 for a display reading of “10000” (Decimal point unimportant).
4.
Select Range 3
rd
and connect to the correspondent ½ scale standard resistor.
Example: If 2KΩ range is selected, connect to a 1KΩ standard resistor.
5.
Adjust RV1 for a display reading equal to the resistor value.
6.
Select Range 4
th
and connect to the correspondent ½ scale standard resistor.
Example: If 20KΩ range is selected, connect to a 10KΩ standard resistor.
7.
Adjust RV2 for a display reading equal to the resistor value.
8.
Check all remaining ranges with the appropriate standard resistors. All ranges must be within
the specifications outlined in the Cal Certificate Sheet.
9.
If the 20Ω range is too low select R27 using the RC Box.
IMPORTANT:
If it is necessary to p
erform step 4.9 go back and forth between the 20Ω and 200Ω range
until both are in spec.
FAILSAFE CHECK
Note: Printed next to each range indicator is the nominal fail-safe current.
1.
Connect the 3458A in the ammeter mode across the current terminals. Place the Alpha 4314 in
the lowest resistance range.
2.
Short out the front two legs of Q4 and record the measured current level for future use.
3.
Repeat this process for each range. The measured value must be less than the value indicated on
the data sheet.
4.
For MΩ
ranges it will be necessary to connect the appropriate calibration resistor and measure
the voltage drop across it. Use Ohm’s Law to calculate the failsafe current.
Range #
0
1
2
3
4
5
6
7
8
Range
Value
2Ω
20Ω
200Ω
2kΩ
20kΩ
200kΩ
2MΩ
20MΩ
200MΩ
STD
Fail-Safe
Current
<16mA
<16mA
<1.8mA
<180μA
<18μA
<1.8μA
<180nA
<18nA
<1.8nA
KRC
Fail-Safe
Current
<8mA
<8mA
<1.8mA
<180μA
<18μA
<1.8μA
<180nA
N/A
N/A
