Arbiter Systems 931A, Руководство по эксплуатации

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GROUND
BEFORE
USE
The purpose of the ground lug is to allow the
chassis to be tied to a safety ground, especially
during battery operation.
CAUTION: The front-panel ground terminal should always be
connected to the safety ground for the circuit under test.
This is especially critical for operation with the line cord
unplugged, since the AC line input safety ground will not be
connected.
3.2.2 Voltage Inputs
The Model 931A features four, front-panel inputs, which can be used for
measurement of AC or DC voltages. These inputs are labeled “A”, “B”,
“C”, and “N” (for phase A, phase B, phase C, and Neutral, respectively).
All four of the inputs utilize identical circuitry,
which allows for measurement of voltages up to 750
Vrms or 1000 Vdc between inputs. The 1 megohm
input voltage dividers are tied to a common point.
Any unused voltage inputs will float at the average
value of the used inputs. Safety-insulated banana jacks are used for the
connections. Measure voltage between any two of the inputs (e.g., “A”
and “N”). Also, the 931A will measure voltage between the input and a
synthesized neutral, which is the average of the voltages at inputs A, B,
and C.
3.2.3 Current Inputs
The Model 931A has three inputs for use in AC current measurement. Each
of the inputs uses a pair of five-way binding posts, and has a maximum
current capability of 20 amps rms. For each pair of terminals, the left-hand
side is positive, and the right-hand side is negative.
For measurement of 3-phase neutral current, the neutral signal ( In ) is
available on Channel 2.
(3.1) In =
−
( Ia + Ib + Ic )
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