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Author: WisdomAugust

Digital Multimeter HDM3055 Series Manual

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 Author| Post time 2024-4-15 08:12:54 | Show all posts
This table gives an additional error for each waveform, to be added to the value from the accuracy
table provided in the instrument's data sheet.

The specifications are valid for CF ≤ 10, provided there is insignificant signal energy above the 300 kHz
bandwidth for voltage, or the 10 kHz bandwidth for current. Multimeter performance is not specified for
CF > 10, or when significant out-of-band signal content is present.
Example
A pulse train with level 1 Vrms, is measured on the 1 V range. It has pulse heights of 3 V (that is, a Crest Factor of 3) and duration 111 ?s. The prf can be calculated to be 1000 Hz, as follows:




file:///C:/Users/ADMINI~1/AppData/Local/Temp/ksohtml6328/wps3.png
Thus, from the table above, this AC waveform can be measured with 0.18 percent additional error.


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 Author| Post time 2024-4-16 08:07:20 | Show all posts
Other Primary Measurement Functions
Frequency and Period Measurement Errors
           
The multimeter uses a reciprocal counting technique to measure frequency and period. This method
generates constant measurement resolution for any input frequency. The multimeter's AC voltage
measurement section performs input signal conditioning. All frequency counters are susceptible to
errors when measuring low–voltage, low–frequency signals. The effects of both internal noise and
external noise pickup are critical when measuring "slow" signals. The error is inversely proportional
to frequency. Measurement errors also occur if you attempt to measure the frequency (or period)
of an input following a DC offset voltage change. You must allow the multimeter's input DC blocking
capacitor to fully settle before making frequency measurements.


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 Author| Post time 2024-4-18 11:42:54 | Show all posts
DC Current

When you connect the multimeter in series with a test circuit to measure current, a measurement
error is introduced. The error is caused by the multimeter's series burden voltage. A voltage is
developed across the wiring resistance and current shunt resistance of the multimeter, as shown
below.



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 Author| Post time 2024-4-19 08:06:10 | Show all posts
Avoid applying signals to unused current input terminals

If signal inputs are applied to terminals not needed for the current measurement, measurement
errors may occur. The unused terminals are still protected but the un-needed signals may interfere
with current measurement. For example, applying inputs to the 3A terminals while making
measurements on the 10A terminals will typically cause errors.

The Hi and Lo sense terminals are not used for many measurements. Applying signals here when
not needed can also cause errors. AC or DC voltages above 15 volts peak on the un-needed sense
terminals are likely to cause measurement errors. If unexpected errors are occurring, signals on the
un-needed terminals is an area to check.


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 Author| Post time 2024-4-20 08:28:03 | Show all posts
Temperature Measurements

Temperature measurements require a temperature transducer probe. The supported probes are
2-wire and 4-wire RTDs, 2-wire and 4-wire thermistors.
Probe Type Choice
RTD's provide very accurate, highly linear relationships between resistance and temperature,
over a range of roughly –200 to 500 °C. There is very little conversion complexity for an RTD
because it is so intrinsically linear. The multimeter provides measurement for the IEC751 standard
RTD, which has a sensitivity of 0.385%/°C.


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 Author| Post time 2024-5-7 08:23:00 | Show all posts
Thermistor Requirements

The DMM converts the measured thermistor resistance to temperature using the Steinhart-Hart
thermistor equation:
1?T = A + B (Ln(R)) + C (Ln(R))3
Where:
A, B, and C are constants provided by the thermistor manufacturer and derived from three
temperature test points.
R = Thermistor resistance in Ω.
T = Temperature in degrees K.


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 Author| Post time 2024-5-8 13:09:50 | Show all posts
Important: Use only a 5 k? 44007-type thermistor. This type thermistor has constants of A = 1.285e-3,
B = 2.362e-4, C = 9.285e-8. Using an incorrect type of thermistor can result in errors greater than 20 °C
for a temperature being measured of 100 °C.
2-Wire vs. 4-Wire Measurements

As with resistance measurements, 4-wire temperature measurements are more accurate, because errors
due to lead wire resistance are completely eliminated. Alternatively, you can use the multimeter’s Null function
to remove the test lead resistance from the measurement (see NULL Reading below).


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 Author| Post time 2024-5-9 13:28:47 | Show all posts
NULL Reading

The DMM allows a separate null setting to be saved for the temperature function. When making
null measurements, each reading is the difference between a stored null value and the input signal.
One application of NULL is to increase accuracy of two-wire resistance measurements by first nulling
the closed–circuit test lead resistance.

Autozero On/Off

Enabling the autozero feature (ON) provides greater accuracy; however, the additional measurement
(of zero) reduces the reading speed.


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 Author| Post time 2024-5-10 08:26:15 | Show all posts
Making High–Speed AC Measurements

The multimeter's AC voltage and AC current functions implement three low–frequency filters.
These filters allow you to trade–off minimum measured frequency for faster reading speed.
The FAST filter settles in 0.025 seconds, and is useful for frequencies above 200 Hz. The
MEDIUM filter settles in 0.625 seconds for voltage and 0.25 seconds for current, and is useful
for measurements above 20 Hz. The SLOW filter settles in 2.5 seconds for voltage and 1.66
seconds for current, and is useful for frequencies above 3 Hz.


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 Author| Post time 2024-5-13 08:15:29 | Show all posts
Edited by WisdomAugust at 2024-5-14 08:37


With a few precautions, you can perform AC measurements at speeds up to 500 readings
per second.

Use manual ranging to eliminate auto-ranging delays. By setting the trigger delay to 0, the
FAST, MEDIUM, and SLOW filters allow up to 500, 150, and 50 readings per second, but with
reduced accuracy because the filter may not fully settle. If the sample–to–sample levels are
similar, little settling time is required for each new reading. Under this specialized condition,
the MEDIUM filter provides reduced accuracy results at 20 readings per second, and the FAST
filter provides reduced accuracy results at 200 readings per second.



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