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DVM & SHUNT Combo
DVM-SHUNT Combo
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Product Introduction
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The DVM-VC890D
is a Laboratory Quality Multimeter, packed with features, and
offered to the hobby enthusiast at an affordable price. This unit
is a must-have for any avid electric modeler.
In addition to an over-sized LCD, the unit is very accurate and
capable of measuring voltage, resistance, capacitance, continuity,
and current all the way up to 20A in one small, attractive package.
Auto Power Off and Peak Hold also included.
The new DVM-SHUNT-60
is a current shunt that provides an economical way to extend the
current (Amps) capability of your existing Digital Volt Meter
(DVM) to 60amps continuous or 100amps for up to 60 seconds. This
simple device connects between your battery pack and ESC and includes
two probe leads that connect to any DVM. Set the DVM to read mVolts
and the number you read on the DVM display correlates directly
to the current draw through your power system as Amps. No guess
work needed! Accuracy depends on the accuracy of the meter to
which the SHUNT is connected.
Key Features:
 DVM-VC890D
- Auto Power Off
- Peak Hold
- Fuse Protected
- Over-sized LCD (1" Digits)
- Quality Construction
- Size: 3.50" x 6.70" x 2.00"
- Measurement Ranges: 2nF - 200uF, 200Ohm - 20MOhm, ACV 2V
- 750V, DCV 200mV - 1000V, AC Current 2mA - 20A, DC Current
20uA - 20A
 DVM-SHUNT-60
- 0.001 ohm resistance for direct readout from a digital voltmeter
(DVM) milliVolt scale
- Handles 60A continuous current, and up to 100A for brief
periods (<1 minute)
- Deans Ultra connectors for attaching to power system components,
and standard probe connectors for attaching to almost any DVM
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Contents
and Operation:
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The Digital Multimeter comes with probe tips, a universal adapter,
and a 9v battery already installed. The two page manual describes
operation, saftety notes, general and technical specifications.
The meter has a large 25mm LCD display and can measure DC volts,
AC volts, DC amps, AC amps, resistance, capacitance, diodes, transisters,
and also has a continuity test with audible tone. The DVM-VC890D
is a Laboratory Quality Multimeter, packed with features, and
offered to the hobby enthusiast at an affordable price. This unit
is a must-have for any avid electric modeler!
The DVM-SHUNT-60 is a 60A Current Shunt for measuring electric
propulsion system current with a standard digital voltmeter. It
comes with a two page manual that fully describes operation, theory
of use, and application in measuring R/C electric power systems.
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The Digital Multimeter
comes with probe tips, a universal adapter, and a 9v battery
already installed.
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The two page
manual describes operation, saftety notes, general and
technical specifications.
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The DVM-SHUNT-60
is a 60A Current Shunt that comes with a two page manual
that fully describes operation
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1. Connect the shunt between the battery and ESC
as shown above.
2. Connect the shunt’s measurement leads to a DVM (red to
+, black to –), such as FMA’s
DVM-VC890D laboratory-quality digital multimeter.
3. Set the DVM to read milliVolts.
4. Important! If the propulsion system is mounted in an aircraft,
secure the aircraft so it will
not move when the propeller is turning. If you are bench-testing
a propulsion system, secure
the motor so it will not move when the propeller is turning.
5. Turn on your transmitter. Move the throttle all the way down
to its full off position.
6. Turn on the ESC and receiver. Stay clear of the propeller!
7. Advance the throttle to maximum, read the DVM display, then
return the throttle to full off.
8. Turn off the ESC and receiver.
9. Turn off the transmitter.
Propulsion system current in Amps = DVM reading in milliVolts.
For example, if the DVM reads 37 milliVolts, then the propulsion
system is drawing 37 Amps.
Principle of operation:
A shunt is a conductor with very low resistance in parallel with
another device, in this case a voltmeter. As current flows through
the circuit, the voltmeter measures the small voltage drop across
the shunt. Since we know the shunt resistance (0.001 Ohms) as
well as the voltage, we can calculate the current using Ohm’s
Law:
current = voltage/resistance ...or in our case... Amps = milliVolts/0.001
How you can use current data:
- Verify that components can handle the current. Your battery
pack, connectors, power wiring and ESC all have maximum current
ratings. Once you know the system’s current draw, check
component specifications to make certain you are not exceeding
maximum current.
- Predict aircraft performance. Many factors determine how
your aircraft will perform in flight. Watts per pound is a simple
calculation that may tell you how a particular airframe and
propulsion system will fly.
- Remove the shunt from your propulsion system, then use the
DVM to measure battery voltage under the same load as used to
measure current. Use this formula to calculate watts per pound:
watts per pound = Volts x Amps / model weight in pounds
Modelers using electric power have developed rough guidelines
relating power to weight.
Your airplane’s performance may vary.
- 30 to 40 watts per pound: level flight
- 40 to 50 watts per pound: take off from smooth surfaces,
climb
- 50 to 75 watts per pound: take off from grass, sport aerobatics
- 75 to 125 watts per pound: pattern aerobatics
- >125 watts per pound: 3D
Application Example:
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The DVM/SHUNT combo was tested on my
Black Horse Decathlon power system using a 4-cell Kokam 3200mAh
pack on the AXI 2826/10 motor with an APC 11x8.5 e-prop. The
speed control is a Jeti 70-amp Opto Advance Plus ESC.
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After measuring the current using the
DVM and SHUNT, I then measured the pack voltage under load at
14.3v using the DVM and probe tips by partially separating the
Deans Ultra connection between the battery pack and the ESC
and using the standard DVM probes.
By multiplying the current by the voltage
under load, we can determine the power level.
Power Level = 48.2amps x 14.3v (under
load) = 689 watts.
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The DVM read 48.2 mV which means 48.2amps
using the SHUNT. I used the HOLD button feature to retain the
measurement while safely throttling down to take the photo.
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By knowing the power level, we can determine the watts per
pound and gain good insight on the expected performance in flight.
By knowing the current at full throttle, we can determine if
the motor and speed control are within operating specifications.
We can also determine if the Lithium pack chosen can safely
deliver the level of current without getting too hot or exceeding
the manufacturers C-discharge rating.
The DVM and SHUNT combo is a valuable combination of tools
that allows us to "see" what is going on in our electric
power system so that we can increase the performance, safety,
and longevity of our investment in R/C.
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