Representante
y distribuidor exclusivo en México de ETS-Lindgren y Amplifier
Research.
Interés General
Algunas preguntas frecuentes sobre los equipos de ETS-Lindgren EMC
What do the dashes on my 2090 display mean?
The dashes across the front panel display signify that the controller is not communicating with it's device (such as the motor base).
Make sure the device (motor base) has AC Power.
Make sure that the fiber optic cable is connected properly per manual specifications.
Ensure that the fiber optic cable is not damaged and the connectors on the motor base and the controller are not broken or damaged.
Can I control an older EMCO turntable and/or mast using a 2090?
Yes. A Retro-Kit is available from EMCO that will allow a 2090 to interface to a 1050/1060 (Tower/Turntable) or a 1070/1080 (Tower/Turntable).
How do I calculate the electric field generated on my antenna?
"Computing Required Input Power for a Given E-Field Level at a Given Distance" application note is available from EMC Test Systems. Please contact a sales representative to receive a copy.
What is the difference between antenna factor and gain?
The antenna factor and the gain can be related to each other with the following expression:
G = 20 Log (F) - AF - 29.79
Where:
G = Isotropic gain in dBi
F = Frequency in MHz
AF = Antenna Factor
How do I calculate the electric field generated in a GTEM?
The basic formula to calculate the field strength in a GTEM! is as follows:
E = (sqr(50 * Pw)) / Hm
Where:
E = Electric field in V/m
= impedance in Ohms
Pw = Power in Watts
Hm = Septum Height in Meters
Note: This formula has a variance of +/- 3 dB. Always assume the worst case electric field when attempting to size an amplifier.
What size of an EUT can a GTEM! support?
The "rule of thumb" is an EUT 1/3 the septum height. There are six GTEM!s available, sized according to septum height. For example, the model 5317 or "1700" has a maximum septum height of 1700mm or 1.7m. Therefore the maximum EUT size can be no larger than 567mm.
How do I correlate my GTEM! to an OATS (Open Area Test Site)?
Testing of radiated emissions is allowable with a GTEM just as long as it has been demonstrated for a "generic" product type that correlation can be shown to an open field site that is registered with the FCC.
The FCC Public Note of December 2, 1993, states, in part: "Acceptable comparison measurement data must be filed... accompanied by an appropriate analysis that demonstrates equivalence with an open area test site........", and
"Validity of calculated correlation coefficients must be supported by statistical analysis"
Once the generic test and comparison analysis is completed and the date is submitted to the FCC and accepted, other similar EUTS may be tested without additional comparisons.
The steps to complete such a process are four-fold:
Preparation and transmittal of a letter to the FCC at: Federal Communication Commission 7435 Oakland Mills Road Columbia, MD 21045
Selection of product to be used as EUT for comparison testing. This step is critical, as the product selected as the generic product will determine how wide an application of the GTEM! will be covered in the original application. Submission of comparative data with the appropriate statistical analysis of that data will be necessary for every "generic" type of product to be tested.
Gather the appropriate data and perform the required calculations. When testing in the GTEM!, three cold-start tests are made. The E-field data is computed, and cable losses, preamplifier gain, and if necessary, instrument calibration must be used in the computations. When testing at an OATS, three cold-start tests are also made. The E-field data is computed and current antenna factors, cable losses, preamplifier and instrument calibration data must be used in the computation. The minimum Data Analyses using dB(uV)/m data in all cases, compute:
a) the average GTEM E-Field values at each frequency
b) compute the average OATS E-Field values at each frequency, c) subtract OATS values from the GTEM! values to get differences as a function of frequency,
d) the mean and standard deviation of the differences as a function of frequency.
When all data has been gathered and all computations completed, a letter is sent to the FCC, requesting approval for the use of the GTEM! for compliance demonstration testing. This letter should include a detailed description of the product or device tested, all test results, and the statistical analyses.
The preceding information was provided by Steve Berger, (Advisory Engineer, Professional Testing Inc. Round Rock, TX)
In relation to your other questions, variations in the measurements taken in a GTEM have been quite often due to the test setup of the EUT being maintained throughout all three orthogonal view positionings of the table/manipulator. It is important that the cables are maintained at a consistent orientation to the plane on which the EUT is placed through all three orthogonal views of the EUT. Failure to do this will result in poor results.
Can I test my three(3) phase EUT with a two(2) line LISN?
No. But a three(3) phase EUT can be tested using two(2) - two(2) line LISNs by setting the LISNs side by side and connect each phase to a line.
What is the pinout and signal definition for the 3816?
Since pin 2 is common, in order to select L1, apply 5 VDC to Pin 1 with respect to common. To select L2, apply 5 VDC to Pin 3 with respect to common. The relay coils in the LISN are rated for TTL levels.
