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<html><head><title>Delta Electronics, Inc. RF Ammeter Systems</title></head>
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<center><img src=../delta1.jpg alt="Delta Electronics, Inc.">
<h2>RF Ammeter Systems</h2></center>
<center><img src="tca-std.jpg" alt="TCA RF Ammeter"></center>
<hr>
<h3>Introduction</h3>
The Transformer Coupled Ammeter (TCA) series of RF Ammeters provides AM broadcasters with an accurate and reliable instrument for measuring common point and antenna base currents. The ammeter uses a toroidal current transformer to obtain a sample voltage proportional to the RF current flowing in a conductor. This voltage sample is connected by a 50 ohm coaxial cable to a temperature compensated rectifier circuit. This circuit converts the RF voltage to a DC voltage which is applied to a linear scale meter, calibrated in RF Amperes, for display of current magnitude. The ammeter provides a DC output voltage to drive a remote indication instrument which may be calibrated against the primary meter and used for remote indication. Ammeters which include relays to remotely control the operation of the meter are also available.
<p>
<h3>Description</h3>
The RF Ammeter system comprises a toroidal current transformer unit, a rectifier/meter unit and an interconnecting coaxial cable. Depending on the RF conductor voltage, the transformer unit may be either the <a href="tctxfmr.htm">TCT-N</a> (10 kV<font size=-2><sub>RMS</sub></font> rating) transformer, the <a href="tctxfmr.htm">TCT-N-HV</a> (20 kV<font size=-2><sub>RMS</sub></font> rating) transformer or the <a href="tctxfmr.htm">TCT-N-XHV</a> (42.4 kV<font size=-2><sub>RMS</sub></font> rating) transformer. These transformer voltage ratings are the RMS equivalent of the peak modulation voltage. Within each TCT type, several versions are available depending on the RF current magnitude. The TCT provides an RF voltage sample directly proportional to the current. The voltage sample is applied to the rectifier/meter unit by a 50 ohm coaxial cable. The rectifier circuit provides a 50 ohm load resistor for proper termination. This circuit converts the RF voltage sample to a DC voltage for meter display. The rectifier filter circuit is designed to follow the modulation envelope accurately on both positive and negative meter excursions. The meter ballistics average the audio content and thus, the meter indicates the RF carrier current. The meter provides a stable reading independent of modulation, but may deflect slightly under high modulation conditions due to carrier shift. A switch on the unit provides local operation of the meter and selects either the high or low scale for dual scale units. The rectifier/meter unit also provides a DC output voltage to drive a remote indicating instrument. When the local switch is in the off position, the rectifier circuit input is disconnected from the RF input and grounded for lightning protection.
<p>
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.
<p>
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.
<p>
<h3>Ammeter Accuracy and Calibration</h3>
The RF Ammeter Systems are capable of measuring RF current with excellent accuracy. The accuracy specification of ±2% full scale is guaranteed over a temperature range of -40° C (-40° F) to +65° C (+150° F) and over a frequency range of 500 kHz to 2000 kHz. By using the linearity chart on the calibration sheet included with the ammeter, the meter accuracy may be improved to within ±1% full scale.
<p>
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 guaranteed 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.
<p>
<h3>Meter Nomenclature</h3>
The TCA-EX and TCA-EXR series of RF Ammeters include a wide variety of scales, scale combinations, and optional features, all of which are uniquely defined in the model designation system.
<p>
<strong>TCA-N-EX:</strong> This 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.
<p>
<strong>TCA-N-EXR and TCA-N/N-EXR:</strong> Meters with the "-EXR" suffix provide an internal relay to remotely disconnect the rectifier circuit input from the RF input and ground the rectifier circuit. The dual scale models include a second relay for changing scales remotely. These relays are operated by a 24 VDC, 25 mA external power supply. The dual-scale system allows selection of any two of the adjacent scale ranges. For example, the TCA-20/40-EXR has a 4 to 20 ampere range on its lower scale, and an 8 to 40 ampere range on its upper scale. A three position toggle switch controls the metering function, where the upper position is for the high scale, the lower position is for the low scale, and the center position grounds the rectifier circuit and turns the meter off.
<p>
<strong>TCA-N-EX-HV:</strong> 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 kV<font size=-2><sub>RMS</sub></font>). 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.
<p>
<strong>TCA-N-EX-XHV:</strong> 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 kV<font size=-2>RMS</font>). 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.
<h3>Installation Drawings</h3>
<a name="list"></a>For case outline, mounting and associated installation dimensions and for interconnection diagrams see the following:
<blockquote>
<a href="tcan.htm">Model TCA-EX/EXR Installation Drawings</a>
</blockquote>
<hr>
<center>
<table border bgcolor=White>
<caption><h3>Available Models</h3></caption>
<tr><td>
<table cellspacing=0 cellpadding=4>
<caption><strong>SINGLE SCALE MODELS</strong></caption>
<tr align="middle"><td width=200>Current Range (A<font size=-2>RMS</font>)<hr></td><td width=200>TCA-N-EX<hr></td><td width=200>TCA-N-EXR<hr></td></tr>
<tr align="middle"><td>1-5</td><td>TCA-5-EX</td><td>TCA-5-EXR</td></tr>
<tr align="middle"><td>2-10</td><td>TCA-10-EX</td><td>TCA-10-EXR</td></tr>
<tr align="middle"><td>4-20</td><td>TCA-20-EX</td><td>TCA-20-EXR</td></tr>
<tr align="middle"><td>8-40</td><td>TCA-40-EX</td><td>TCA-40-EXR</td></tr>
<tr align="middle"><td>16-80</td><td>TCA-80-EX</td><td>TCA-80-EXR</td></tr>
<tr align="middle"><td>32-160</td><td>TCA-160-EX</td><td>TCA-160-EXR</td></tr>
<tr align="middle"><td colspan=3><hr><strong>DUAL SCALE MODELS</strong></td></tr>
<tr align="middle"><td>Current Range (A<font size=-2>RMS</font>)<hr></td><td colspan=2>TCA-N/N-EXR<hr></td></tr>
<tr align="middle"><td>1-5 and 2-10</td><td colspan=2>TCA-5/10-EXR</td></tr>
<tr align="middle"><td>2-10 and 4-20</td><td colspan=2>TCA-10/20-EXR</td></tr>
<tr align="middle"><td>4-20 and 8-40</td><td colspan=2>TCA-20/40-EXR</td></tr>
<tr align="middle"><td>8-40 and 16-80</td><td colspan=2>TCA-40/80-EXR</td></tr>
<tr align="middle"><td>16-80 and 32-160</td><td colspan=2>TCA-80/160-EXR</td></tr>
<tr><td colspan=3><hr><ul>NOTE 1: All models can be supplied with high voltage transformer by appending -HV to model number for 20 kV<font size=-2><sub>RMS</sub></font> transformer voltage rating or by appending -XHV to model number for 42.4 kV<font size=-2><sub>RMS</sub></font> transformer voltage rating. Examples: TCA-10/20-EXR-HV specifies a 10A and 20A dual scale meter with 20 kV<font size=-2><sub>RMS</sub></font> transformer and TCA-160-EXR-XHV specifies a 160A single scale meter with 42.4 kV<font size=-2><sub>RMS</sub></font> transformer.</ul></td>
</tr></table>
</td></tr></table>
</center>
<p><hr>
<center>
<table border=2 cellpadding=8 bgcolor=White>
<caption><h3>RF Ammeter Accessories</h3></caption>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#remote">TCA-N-EXM</a></td><td>Remote Meter Set, Single Scale (3" or 4" meters available)</td></tr>
<tr><td align="middle" valign="top"> <a href="tcaacces.htm#remote">TCA-N/N-EXM</a> </td><td>Remote Meter Set, Dual Scale (3" or 4" meters available)</td></tr>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#stdpanel">TCA-EXMP</a></td><td>Standard Meter Panel (Mounts up to four 3" remote meters or three 4" remote meters)</td></tr>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#encpanel">TCA-EXMCP</a></td><td>Enclosed Meter Panel (Mounts up to four 3" remote meters or three 4" remote meters and includes TCA-PS2 power supply and provision for TCA-IBA amplifier)</td></tr>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#amplifier">TCA-IBA</a></td><td>Integrating Buffer Amplifier Assembly</td></tr>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#power">TCA-PS2</a></td><td>Power Supply (120/240 VAC, 50/60 Hz input, ±15 VDC/100 mA and 24 VDC/500 mA outputs)</td></tr>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#bushing">TCA-LS</a></td><td>Conductor Bushing (Increases standard TCT transformer voltage rating to 15 kV<font size=-2><sub>RMS</sub></font>)</td></tr>
<tr><td align="middle" valign="top"><a href="tcaacces.htm#bracket">TCA-MB</a></td><td>Mounting Bracket (Mounts one or two standard TCT transformers or one meter unit)</td></tr>
<tr><td align="middle" valign="top"><a href="tca1data.htm">TCA-TS</a></td><td>Transient Suppressor Assembly (Type N T-Adapter with connector mounted suppressor)</td></tr>
<tr><td align="middle" valign="top">TCA-RFR</td><td>EMI/RFI Shielded Enclosure (Houses TCA-EXR rectifier/meter unit and protects from dust, dirt, oil and water)</td></tr>
</table></center>
<p><hr>
<center>
<table border cellpadding=10 bgcolor=White>
<caption><strong>SPECIFICATIONS</strong></caption>
<tr><td><table cellpadding=4 cellspacing=0>
<tr><td><strong>Frequency Range:</strong></td><td>0.5 to 2 MHz</td></tr>
<tr><td><strong>Current Ranges:</strong></td><td>1 to 160 Amperes, see table of available models</td></tr>
<tr valign="top"><td><strong>Accuracy (Direct Reading):</strong></td><td>
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.</td></tr>
<tr><td><strong>Current Transformer:</strong></td><td>Shielded Toroidal Current Transformer (TCT series)</td></tr>
<tr valign="top"><td><strong>Conductor Voltage to Ground<br>(RMS Equivalent of Peak Modulation Voltage): </strong>
</td><td><table cellpadding=0 cellspacing=0>
<tr><td>TCT-N Series:</td><td>10 kV<font size=-2><sub>RMS</sub></font></td></tr>
<tr><td>TCT-N-HV Series:</td><td>20 kV<font size=-2><sub>RMS</sub></font></td></tr>
<tr><td>TCT-N-XHV Series: </td><td>42.4 kV<font size=-2><sub>RMS</sub></font></td></tr>
</table></td></tr>
<tr><td><strong>Electric Field Rejection:</strong></td><td>>100 dB</td></tr>
<tr valign="top"><td><strong>Rectifier Circuit:</strong></td><td>Temperature compensated, linearized silicon rectifier circuit.</td></tr>
<tr valign="top"><td><strong>Temperature Range:</strong></td><td>-40° C (-40° F) to +65° C (+150° F) with rated accuracy</td></tr>
<tr valign="top"><td><strong>Lightning Protection Switch:</strong></td><td>
Toggle switch mounted on meter unit disconnects and grounds rectifier circuit. Dual range models have 3 way switch
with center off position.</td></tr>
<tr valign="top"><td><strong>Interconnecting Cables:</strong></td><td>
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.</td></tr>
<tr valign="top"><td><strong>Indicating Instrument:</strong></td><td>
Taut band, mirror scale, ruggedized 1% linearity meter with 2.75 inch scale length</td></tr>
<tr valign="top"><td><strong>Scale Expansion:</strong></td><td>Linear over useful range.</td></tr>
<tr valign="top"><td><strong>Scale Divisions:</strong></td><td>
Scale divisions above 1/5 full scale not greater than 1/50 full scale (FCC specification)</td></tr>
<tr valign="top"><td><strong>Modulation Characteristics:</strong></td><td>
Indicates average RMS current (Minimum modulation effect. Will show carrier shift.)</td></tr>
</table>
</td></tr></table>
</center>
<hr>
For additional information on any of our products, please contact <a href="mailto:[email protected]">Sales</a> to discuss your particular requirements:<br>
<center><table cellpadding=20>
<tr valign=top>
<td><strong>Delta Electronics, Inc.<br>
5730 General Washington Drive<br>
P. O. Box 11268<br>Alexandria, VA 22312<br><br></strong></td>
<td><strong>Phone: (703) 354-3350<br>
U.S. Toll Free: 1-800-8-DELTA-8 (1-800-833-5828)<br>
Fax: (703) 354-0216<br>
<address>www.deltaelectronics.com</address>
Email: <a href="mailto:[email protected]">[email protected]</a></strong></td>
</tr>
</table></center><hr>
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<font size=1>The Delta Electronics logo is a registered trademark of Delta Electronics, Inc.</center></font>
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