The RF Ammeter series encompasses both single and dual scale models to provide RF current measurement over the range from 5 Amperes full scale to 160 Amperes full scale. These current ranges follow the FCC rules for linear scale meters. The minimum normal reading must be at least 1/5 full scale, and the maximum reading must not exceed full scale under normal power variations or modulation. Since the TCA series meters do not respond to modulation, it is practical to use the meters up to 95% of full scale.
The standard interconnecting coaxial cable length is six feet. Longer coaxial cable lengths and double shielded coaxial cable are optionally available for any TCA system for high RF field conditions and for RF radiation exposure reduction.
Ammeter Accuracy and Calibration
Every RF Ammeter is calibrated and sealed at the Delta laboratory. Each RF Ammeter is calibrated at a frequency of 1 MHz. The flat frequency response and compensated temperature characteristics of the ammeter assure accurate current measurement. The calibration of the RF Ammeter is warranted for a period of one year under normal use conditions. Excluding damage due to lightning, Delta will recheck the calibration and make repairs, if necessary, without charge during this period. These services are available at a nominal charge at any time thereafter.
TCA-N-EX: The TCA-EX RF Ammeter series has been superseded by the TCA-EXR series. Information on the TCA-EX series is included for legacy equipment applications. The TCA-EX model is a single-scale meter with external output. The system consists of a current transformer, a six foot coaxial cable, and a meter enclosure housing the meter movement, rectifier circuitry, and external output connector. The external output can be used in conjunction with a series 10K Ohm variable resistor connected to a second meter to provide for remote metering. The external output may also be used to drive automatic logging, remote control, or ATS equipment. A two-position toggle switch mounted on the front of the meter box turns the circuit on and off, and when switched off, protects the rectifier circuit against lightning damage. A spring-loaded, momentary contact toggle switch is optionally available to prevent leaving the ammeter in the on position.
TCA-N-EXR-HV: The suffix “HV” appended to any of the TCA series model numbers specifies that the current transformer supplied with the meter is the high voltage type rated for operation at conductor voltages as high as 28 kV peak (20 kVRMS). The transformer provides a 3.38″ diameter clearance hole for the antenna conductor. A 0.75 to 1.0″ diameter tubular conductor centered in the clearance hole provides maximum voltage capability. Corona rings which increase the voltage rating by approximately 5% are available as a factory installed option.
TCA-N-EXR-XHV: The suffix “XHV” appended to any of the TCA series model numbers specifies that the current transformer supplied with the meter is the extra high voltage type rated for operation at conductor voltages as high as 60 kV peak (42.4 kVRMS). The transformer provides a 6.0″ diameter clearance hole for the antenna conductor. A 2.0 to 2.25″ diameter tubular conductor centered in the clearance hole provides maximum voltage capability.
|Frequency Range:||0.5 to 2 MHz|
|Current Ranges:||1 to 160 Amperes, see table of available models|
|Accuracy (Direct Reading):||Better than 2% of full scale from 20 to 100% of full scale. Calibration curve supplied for greater accuracy. Accuracy may be reduced if RF currents induced by other stations are 5% or greater than the current to be measured.|
|Current Transformer:||Shielded Toroidal Current Transformer (TCT series)|
|Conductor Voltage to Ground (RMS Equivalent of Peak Modulation Voltage):||TCT-N Series: 10 kVRMS|
|TCT-N-HV Series: 20 kVRMS|
|TCT-N-XHV Series: 42.4 kVRMS|
|Electric Field Rejection:||>100 dB|
|Rectifier Circuit:||Temperature compensated, linearized silicon rectifier circuit.|
|Temperature Range:||-40° C (-40° F) to +65° C (+150° F) with rated accuracy|
|Lightning Protection Switch:||Toggle switch mounted on meter unit disconnects and grounds rectifier circuit. Dual range models have 3 way switch with center off position.|
|Interconnecting Cables:||Standard six foot, 50 ohm coaxial cable supplied to connect transformer unit to rectifier/meter unit. Longer cable lengths and double shielded coaxial cable are optionally available.|
|Indicating Instrument:||Taut band, mirror scale, ruggedized 1% linearity meter with 2.75 inch scale length|
|Scale Expansion:||Linear over useful range.|
|Scale Divisions:||Scale divisions above 1/5 full scale not greater than 1/50 full scale (FCC specification)|
|Modulation Characteristics:||Indicates average RMS current (Minimum modulation effect. Will show carrier shift.)|
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