Cal of dut 4

Returns to Port 1. The remainder of the signal passes through the DUT and enters Port 2 of the VNA. Two receivers at Port 1 measure both incident and reflected waves and a receiver at Port 2 measures the wave entering there. Copper Mountain Technologies1. A VNA can separate and measure incident and reflected signals; therefore, it’s able to directly determine reflection coefficients. Shown here is a simplified VNA measurement setup.We call the ratio of the incident wave to the reflected wave—the reflection coefficient—S11. The ratio of the signal entering Port 2 to the incident signal leaving Port 1 is called S21. Figure 1 shows both.In the real world, there would be reflections from within the DUT and another reflection at the output connector, but they’re not shown to keep the diagram simple.There are only a few possibilities for what can happen to the incident signal:It can be reflected back to the source in one or more places.It can be dissipated as heat within the DUT.It can be radiated away by the DUT.It can pass through the DUT and make its way to Port 2.If the signal isn’t dissipated or radiated, then a direct relationship exists between S21 and S11. That is:This is simply a conservation of energy statement. Signals that aren’t being reflected must pass through the DUT. What Does a VNA Measurement Look Like? In the actual measurement shown below, a 4-GHz bandpass filter is connected to an SC5090, a 9-GHz 2-port analyzer (Fig. 2).Copper Mountain Technologies2. In the actual measurement depicted in Figure 1, a 4-GHz bandpass filter is connected to an SC5090, a 9-GHz two-port analyzer.The purple trace in Figure 3 shows S21 in log magnitude format. This is the signal that passes through the filter from Port 1 to Port 2. Markers 2 and 3 indicate the points at which the filter attenuation is 60 dB. Marker 1 is set to the middle of the filter, where most of the signal is passing with little attenuation.Copper Mountain Technologies3. Shown are the measurement results for the 4-GHz bandpass filter.In this chart, the dB scale on the

Between the device under test and the reference standard used. The ratio is the accuracy (or uncertainty) of the device under test compared to the one of the reference standard. We commonly hear about using a TAR ratio of 4 to 1, which means that the reference standard is 4 times more accurate than the device under test (DUT). I.e. the accuracy specification of the reference standard should be 4 times better (or smaller) than the one of DUT.The idea of using certain TAR/TUR (for example 4 to 1) is to make sure that the reference standard is good enough for the purpose.It is good to remember that for example the TAR only takes into account the accuracy specifications of the instruments and does not include all the uncertainty components of the calibration process. Depending on the type of calibration, sometimes these uncertainty components can be larger than the accuracy specifications.It is recommended to always calculate the total uncertainty of the calibration.More detailed information on the calibration uncertainty, please read the related blog post: Calibration uncertainty for dummiesWhat do tolerance limit, out of tolerance, and pass/fail calibration mean?Most often when you calibrate an instrument, there is a tolerance limit (acceptance limit) set in advance for the calibration. This is the maximum permitted error for the calibration. If the error (difference between DUT and reference) at any calibrated point is larger than the tolerance limit, the calibration will be considered as “failed.”In the case of a failed calibration, you should take corrective actions to make the calibration pass. Typically, you will adjust the DUT until it is accurate enough.More detailed discussions on calibration tolerance can be found in the blog post: Calibration out of tolerance: What does it mean and what to do next? What are As Found and As Left

Resistance and (if the standard requires) ground bond tests. Electrical motors, transformers and other such devices will likely include insulation resistance tests.Periodic inspection and calibration of test equipment is a standard requirement to maintain NRTL certification. Agency inspection will include check of hipot instrument calibration. This “cal cert” is typically required on an annual basis. (UL and other NRTLs require compliance certification with ISO17025.) Another common requirement prescribed by most NRTLs is a daily functional test of the hipot equipment.Dielectric Withstand – HipotThe basic hipot test applies a high voltage from the conductors to the chassis of the device-under-test (DUT). This test is often referred to as a “dielectric” or “voltage” withstand. Its purpose is to confirm that the insulation and isolation of the non-conducting surfaces from the operating voltage is sufficient to avoid a shock hazard. The typical specification for this test ins 1000V + 2 x normal operating voltage.Both AC and DC hipot tests are possible and, in general, the test should use the same type of voltage as it would be during normal operation. However, if a DC hipot test is used on an AC circuit, the hipot voltage should be two times the peak (2 x 1.4 x RMS) + 1000VDepending on the applicable standard, units pass this test if either:the leakage current measured is less than the maximum allowable currentno breakdown occurs, i.e., no sudden and uncontrolled flow of currentFour double-insulated products, higher voltages will often be specified in the test standard. In addition, this class of device typically requires special fixturing to connect the non-conductive outer shell to a conductive element.Defects that are often detected with the hipot test include contamination (dirt, debris) and lack of proper spacing (creepage and clearance) of components. Creepage is measured across surfaces, clearance is the air gap between

Insure a low impedance path to the panel ground and earth bonded ground. Operator injury may result if the hipot tester is not connected to earth ground properly.The work area and bench surface should consist of non-metallic materials, which means that metal work surfaces should be avoided, and no metal objects should be placed between the operator and DUT. All other metal objects should be grounded or be out of the test area all together. An ESD mat is not a recommended platform for your test station, as it may cause erroneous readings for leakage and is unnecessary in this application. In addition, the test equipment should provide for immediate and safe removal of the output voltage using internal discharge circuitry at the conclusion of the test or if the test is interrupted. Never remove power for the hipot tester. If there is a power interruption, use extreme care in any contact with the DUT. The safest approach is to leave the DUT connected to the hipot tester until power is restored and the tester can conduct its discharge function.Operator Safety ConsiderationsThe test station should have sufficient space for the tester and the DUT without the operator having to reach over the DUT to access the tester. The tester should be at least three inches away from the wall to provide proper airflow for the unit. Ideally the DUT should be isolated from the operator and tester. For larger DUTs, which are wheeled to the test station, the cart should be non-conductive and having locking wheels. (This also applies if the tester needs to be wheeled to the DUT.) Keep the area clean and neat and arrange the equipment so that it is easy and safe for the operator to use.There are many safety features that can be added to