XDM Series 4 1/2 Bench Multimeter

XDM Series 4 1/2 Bench Multimeter

- 4 inch 480 x 320 pixels high resolution LCD - reading rates up to 150 readings/s - true RMS AC voltage / current measurement - dual line display supported - the change trend analysis accessible via special chart mode - SCPI supported - remote control, and data-sharing possible via LAN, USB, RS232 port, and WiFi* * WiFi module is optional - multi- IO interface: USB Device / Host, RS232, LAN, and ext. trigger input

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XDM Series 4 1/2 Bench Multimeter

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Dual display


Dual display enables two kinds of data display at the same time. For example, as figure shows, the multimeter shows the DC and AC voltage at the same time. Can also switch to current. This expand the measurement method for industrial and laboratory field. 


How to measure the frequency bandwidth?

Combined with the spectrum analyzer software structure, in the test of occupied bandwidth, the parameters that need to be considered include: frequency, bandwidth, resolution bandwidth, video bandwidth, detection mode, number of points, percentage of occupied power, and x dB. Since the measured transmitter signal is usually noise-like, the video bandwidth should be set to more than 10 times the resolution bandwidth during the test. The detection mode is set to sample or rms detection.

According to the test requirements of the occupied bandwidth measurement, the function points implemented in the function design process mainly include the measurement of the occupied bandwidth and the measurement of the xdB bandwidth.

Occupied bandwidth

According to ITU regulations, occupied bandwidth refers to a bandwidth in which the average power transmitted under its lower frequency limit and above the frequency upper limit is equal to the specified percentage of the total average power of a given transmission.

Normally, β/2 is 0.5%, and the user can also set the desired value. In the calculation, the power P(f) is integrated along the entire bandwidth along the frequency, and the total power ΣP in the entire bandwidth can be obtained, that is, the total power is the area under the P(f) curve; then the total power is obtained. For two frequency points of 0.5% and 99.5%, then the width between these two frequency points concentrates the occupied bandwidth value of 99% of the total power.

What is the Harms Caused by the Failure of Grounding from Instrument?

In most measurement test systems, the nature of grounding can be basically divided into four categories:

1. Electrical grounding: Originally a conductive connection between the circuit and the earth. However, in the electronic equipment manufacturing industry, the meaning of the word has been relaxed to a point or points used as a zero voltage reference;

2. Power ground: Provide the return path of the current of the power required by the instrument;

3, the Signal Ground: all signal current reference point and return path;

4, Shielded Ground: usually the instrument's metal shell and cable shielding.

A good grounding system will reduce a lot of unnecessary troubles in measurement. The equipment and equipment must be properly used to ensure a good grounding. Good grounding has multiple purposes. The most demanding safety, and the pursuit of a stable circuit, are mainly The following points:

1. The machine is grounded. Under the condition of leakage, the instrument housing can not be charged and the use is safer;

2. Create a zero voltage reference point or a loop path for the integrated signals to achieve normal measurement purposes;

3, good grounding can effectively shield the interference of electric and magnetic fields, including external interference to the instrument, instrument power to the measurement of interference, the instrument to the outside interference

How to understand the spec of “Holdoff” for oscilloscope?

Holdoff (trigger holdoff) means discontinued input trigger signal for a while (holdoff period), during the period, the oscilloscope will not trigger even there is input signal meet the trigger condition. It will represent by percetage for whole of record length or for the whole LCD.

The function of Trigger in oscilloscope is to show the waveform steady, Holdoff function is the same purpose especially to trigger no-repeat signal which meet the trigger condition in long repeat period. 

How to understand  bandwidth in oscilloscope indicators?

Bandwidth is a base indicators for oscilloscope,the same as amplifier bandwidth,it is called  -3dB point,which is input sine wave at oscilloscope,the frequency amplitude is reduced to 70.7% of the actual amplitude is called the bandwidth.In other words,if you measure 1V 100M sine wave and use 100M bandwidth oscilloscope,the amplitude just have 0.707V,it is for sine wave situation.so when we choose oscilloscope,in order to reach measure accuracy,that should choose  maximum signal frequency is 5 times the bandwidth