MFJ MFJ-854 User Manual
Introduction
Congratulations on purchasing the MFJ-854 RF-Current Meter. The MFJ-854 is designed for measuring current distribution on antenna elements and radials, and for checking common-mode current levels on coaxial feedlines and grounds. It also works well for tracking down RFI-causing current on household wiring and cables. Here are some important features we think you'll like:
Wide Range: Measures RF current from as little as 1 mA to 3 Amps in six ranges. Full HF Coverage: Accurate from 1 MHz to 30 MHz and beyond.
Low Interaction: Sense coil has minimal effect on circuits under test. Large Cable Capacity: Accepts cables up to approximately 1/2" in diameter. Accurate: Diode-compensated Op-Amp delivers improved meter linearity. Rugged: Built to last with a sturdy all-aluminum case and G-10 pc board.
Battery Saver: Press-to-test power circuit turns unit off automatically after 15 seconds. Long Battery Life: Meter draws 3-mA, battery's service life approaches shelf life. Handheld Size: Weighs 11 ounces, only 2.3" x 1.6" x 6.5" (including sense coil).
Controls and Locations
1
Cable
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3 |
100mA 300mA |
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30mA |
1A |
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<30mA |
3A |
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Adj |
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Ampres |
Sensitivity Power On
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5
MFJ-854
6 |
9-V |
1.Sense Coil: Clamps onto conductor under test, accepts diameters to around 1/2" .
2.Meter: Calibrated scale indicates readings in mA or Amps.
3.Range: Selects from six measurement ranges.
4.Sensitivity: Works on <30 mA range, adjusts gain for low-level measurements.
5.Power On: Momentary switch applies power, activates 15-second power-off delay.
6.Battery Clip: Accepts any standard 9-V flat-pack battery.
Battery Installation and Replacement: Use any fresh 9-volt flat-pack type battery (not supplied). To install, remove screw from each side of case and gently separate two halves. Install 9-volt battery on snap clip, then slip into retainer (see previous drawing). To prevent damage from battery leakage, always remove battery when storing meter for prolonged periods.
Important Note: Always remove the battery when storing your unit for long periods.
Operating Instructions
Using the Sense Coil: The sense coil snaps over wires and cables, as shown below. To unlatch, squeeze the nylon carrier between thumb and forefinger--applying opposing pressure. The coil's top section should move forward slightly. With pressure applied, lift up to open. Position the wire or cable inside the core opening. Close the lid over the cable, pressing down until latch clicks shut.
Unlatch |
Press |
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Lift |
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Click! |
1 |
2 |
3 |
Meter: The meter is scaled from 0 to 100. On the 100-mA range, readout is direct (100 = 100 mA). On the 1-A range, move the decimal point 2 places to the left (100 = 1.00 A). To convert meter readings made on the 30 mA, 300 mA, and 3-A ranges, multiply accordingly. For example, a reading of 85 on the 300-mA range equals 300 x .85, or 255 mA. The chart below will help you estimate readings quickly:
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Range |
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Meter |
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30 mA |
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100 mA |
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300 mA |
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1 A |
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3 A |
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10 |
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3 |
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10 |
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30 |
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0.1 |
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0.3 |
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20 |
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6 |
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20 |
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60 |
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0.2 |
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0.6 |
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30 |
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9 |
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30 |
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90 |
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0.3 |
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0.9 |
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40 |
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12 |
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40 |
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120 |
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0.4 |
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1.2 |
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50 |
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15 |
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50 |
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150 |
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0.5 |
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1.5 |
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60 |
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18 |
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60 |
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180 |
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0.6 |
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1.8 |
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70 |
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21 |
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70 |
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210 |
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0.7 |
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2.1 |
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80 |
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24 |
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80 |
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240 |
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0.8 |
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2.4 |
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90 |
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27 |
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90 |
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270 |
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0.9 |
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2.7 |
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100 |
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30 |
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100 |
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300 |
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1.0 |
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3.0 |
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The <30 mA range is uncalibrated and meter readings represent a relative indication only. It is normal, at high sensitivity, to see some residual meter reading (up to 15%).
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