UEi Test Instruments DL235 - Manual (Page 5)

Zero Adjustment by the Microprocessor
To initiate the zero adjustment procedure, press the “HOL D” push-button
for 2 seconds. Then, th meter beeps and the display reads zero just after
the microprocessor memorized the right preceding display value that is
used for calculating the exact DC amperes measurement value when
measuring the DC amperes of a current-ca r rying conductor.
When measuring the DC amperes of a current-ca r rying conductor, the
DC amperes value has a positive or negative polarity according to the
direction of current-ca r rying. This value is positive when the current
f l ows through the conductor in the forward-moving direction of a
right-hand threaded screw. And it is negative when the current flow s
through the conductor in the backward-moving direction of a right-hand
threaded screw.
Measuring Frequency
To enable the frequency measured mode, press the “Hz” push-button.
This meter displays “Hz, DUAL, and AUTO” (Fig 4). The frequency of
the current flow is displayed. AUTO (autoranging) is applied to the bar
graph, which represents rms value of the current flow. When in AUTO,
frequency measurement uses an auto trigger threshold based on
one-half of the peak current measurement. This provides the best
sensitivity and noise immunity.
To select a fixed 40A or 400A bar graph display (AUTO is no longer
displayed), press the “RANGE” push-button. With a fixed 40A or 400A
scale, fixed trigger thresholds are imposed for frequency readings.
The thresholds are 6A (40A scale) or 40A (400A scale). The frequency
display is 0.0 Hz when a trigger threshold is not reached.
Press the “RANGE” push-button for 2 seconds and then release in
order to return to autoranging mode. This meter acknowledges with a
beep sound and displays “AUTO” on the digital display. Press the other
function “A or V or Ω or “ push-button to exit the frequency mode.
Using Data Hold
To freeze the digital display reading (HOLD is not applied to the bar
graph), press the “HOLD” push-button. is displayed when
“HOLD” is enabled (Fig 5).
When “HOLD” is used while measuring frequency, “RANGE” can be
changed only for imposing trigger thresholds of 6A on the 40A scale,
and 40A on the 400A scale. The frequency reading will be 0.0 Hz when
“HOLD” is released, if the trigger threshold is not reached.
When in the “HOLD” mode, this meter function can be changed from
the held function to one of the other functions, when “HOLD” is
automatically released.
Press the “HOLD” push-button again ( is no longer displayed)
in order to exit “HOLD”.
Press the “RANGE” push-button for 2 seconds and then release in
order to autoranging mode. This meter acknowledges with a beep
sound and displays “AUTO” on the digital display.
Measuring AC/DC Voltage
Press the “V” push-button to enable the voltage measurement mode
and then select AC or DC by toggling the “AC/DC” push-button. The
meter defaults in the autoranging mode and displays “V, AC and
AUTO”. AUTO (autoranging) is applied to the bar graph (Fig 6).
To measure voltage, connect this meter in parallel with the load or
circuit under test. Each of the three AC/DC voltage ranges presents
an input impedance of approximately 10 MΩ in parallel with less
than 100 pF.
Measurement errors due to circuit loading can result when making
either AC or DC voltage measurement on circuits with high source
impedance. In most cases, the error is negligible (0.1% or less) if the
measurement circuit source impedance is 10 Kilohms or less.
Measuring Resistance
Press the “Ω” push-button to enable the resistance measurement mode.
This meter defaults in the autoranging mode and displays “KΩ” and
“AUTO.” And also the off-scale arrow of the bar graph blinks and the
digital display reads “OFL” (Fig 7).
AUTO (autoranging) is applied to the bar graph.
This meter measures resistance by comparing the internal reference
resistance given by a resistor array with the unknown resistance to be
measured. Remember, the resistance displayed by this meter is the total
resistance through all possible paths between the probes. This explains
why in-circuit measurement of resistors does not often yield the ohms
value indicated by the resistor’s color code.
CAUTION!
Turn off power on the test circuit and discharge all capacitors before
attempting in-circuit resistance measurements. If an external voltage is
present across a component, it will be impossible to take an accurate
measurement of the resistance of that component.
DL235-MAN P. 4
HOLD
HOLD
(Fig 4)
(Fig 5)
(Fig 6)