Tektronix Type 130, Instruction Manual

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AA
6-1
Fig. 6.1. The S-30 Delta Standards.
The S-30 Delta Standards provides a means for calibrat-
ing the Type 130 L-C Meter. The accuracy of the S-30 is
±1% or better on all ranges.
The S-30 provides seven calibrated capacitance ranges,
two precision resistors, and one standard inductance of 300
μ
H at 140 kc.
Equipment Required for Calibration of Delta
Standards
A commercial impedance bridge with tolerances of ± one
quarter of one percent for capacitance, and one per cent for
inductance.
Inductance Standardizer, to be constructed from the fol-
lowing specification in the circuit diagram preceding all
sections on the S-30 Delta Standards. The value of the
capacitor and resistor must be within 2% of those shown.
Figure 6-2 is a pictorial representation of the completed
Inductance Standardizer.
Operation
Only the stray capacitance of the connector and switch
assembly is in the circuit in the
–3 μμ
fd position. The
actual capacitance of these strays is approximately 10 to
20
μμ
fd. No effort is made to standardize this value. As
the switch is rotated, capacitors are switched into the cir-
cuit to provide a change (or "Delta”) of capacitance as in-
dicated. In the 0
μμ
fd position, an additional 3
μμ
fd has been
added in addition to the strays.
Calibration of Capacitance Ranges
Calibration of the capacitance ranges is possible with
most commercial bridges. The procedure is to measure the
capacitance of the S-30 in the
–3 μμ
fd position, then switch
to the 0
μμ
fd position
and determine if the “Delta” change is
3
μμ
fd ±1%. Adjustment of C-2 will be necessary if not
within tolerance. Continue to switch to each range and
measure the capacitance, adjusting the trimmer as indicated
in Table I to give the correct “Delta” changes.
TABLE I
Switch position Typical Value Adjustment
–3 μμ
fd 13
μμ
fd None
0
μμ
fd 16
μμ
fd C-2
+3
μμ
fd 19
μμ
fd C-4
+10
μμ
fd 26
μμ
fd C-6
+30
μμ
fd 46
μμ
fd C-7
+100
μμ
fd 116
μμ
fd C-9
+300
μμ
fd 316
μμ
fd C-11
Calibration of Resistance Ranges
Two precision resistors of identical manufacture are used
ro standardize the resistance compensation. These can be
checked for resistance value with any reliable bridge. If
either resistor is out of tolerance, it is advisable to change
both to maintain the balance of capacity, unless a resistor
of similar manufacture is available.
Calibration of Inductance Range
Standardization of the 300
μ
H inductance is somewhat
complicated since its value cannot be read directly with a
“Bridge” type device, since these generally do not operate
at 120
–150 kc. Since L15 has a powdered iron core, its