U1270 Datasheet, PDF (2/19 Pages) Agilent(Hewlett-Packard) – Agilent U1270 Series Handheld Digital Multimeters

Key functions
Low Impedance (Z_LOW)
The U1272A is a dual input impedance digital multimeter. The DMM’s high input impedance is preferred in most electrical
measurements because it would not load the circuit under test. However, to obtain accurate measurements on circuits
that may contain stray voltages, the U1272A’s 2 kΩ low impedance function comes in handy. Stray voltages are usually
found in non-energized electrical wiring adjacent to powered wires due to capacitive or inductive coupling between these
wires. When a pair of test leads is placed between the open circuit and neutral conductor, the circuit is then complete
and forms a voltage divider in conjunction with the input impedance of the multimeter. High input impedance multimeter
is sensitive enough to measure voltage coupled into the disconnected conductor, thus giving an inaccurate indication of
a live conductor. The low impedance function serves to eliminate false readings by dissipating the stray voltages, thus
improves safety and measurement efficiency during voltage.
Figure 1: U1272A helps you identify the presence of stray voltage on a disconnected wire running parallel with the wire
powering up the VFD to an industrial motor. The image on the right shows the U1272A in low impedance mode.
Low Pass Filter (LPF)
The U1270 series offers a 1 kHz LPF or Low Pass Filter to provide accurate Variable Frequency Drive (VFD) output
measurement. This function eliminates high frequency noise and harmonics. This ensures the efficiency of your motor
filter as well.
Figure 2: Comparison of voltage output from industrial motor VFD without and with Low Pass Filter functionality.
Smart Ω
The U1272A provides an additional 30 Ohm range for low resistance measurement. This Smart Ω function is available
for ranges of 30 Ohm to 300 kOhm. It enhances measurement accuracy with offset compensation by removing residual
DC voltages of up to 1000 mV induced by ground current and thermal EMF. This function also enables ‘live’ resistance
measurement without isolating the measurement circuit. With this, you will be able to obtain leakage current using the
secondary display.
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