RC watt's up WU100 User manual

"Watt's Up" & "Doc Wattson" Watt Meter and
Power Analyzer User's Manual
Model WU100 v2
*** Please visit our website for the latest version of this manual ***
Visit our website: "Watt's Up" Watt meter www.rc-electronics-usa.com
Revision 1 7 1
9/1/2007

Notices
Copyright
Copyright © 2004-2007 by RC Electronics, Inc All rights reserved No part of this manual
may be reproduced or transmitted in any form or by an means, analog, digital, electronic or
mechanical, including imaging, photocopying and recording, for any purpose other than the
purchaser's personal use without the written permission of RC Electronics, Inc , 2980 E
Capitol Expy #50-194, San Jose, CA 95148
Trademarks
Watt's Up and Doc Wattson are trademarks of RC Electronics, Inc
All other brand and product names mentioned in this manual are trademarks or registered
trademarks of their respective owners
Changes
The material in this manual is for information only and is subject to change without notice
While reasonable efforts have been made in the preparation of this manual to ensure its
accuracy, RC Electronics, Inc assumes no liability resulting from errors or omissions in
this manual, or from the use of information contained herein
RC Electronics, Inc reserves the right to make changes in the product design without
reservation and without notification to its users
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Table of Contents I
1 INTRODUCTION..............................................................................................................................3
1 1 WHAT IT DOES 3
1 2 BENEFITS 3
2 FEATURES AND SPECIFICATIONS............................................................................................4
2 1 FEATURES 4
2 2 SPECIFICATIONS TABLES 4
3 SAFETY PRECAUTIONS................................................................................................................5
3 1 SAFE OPERATION LIMITATIONS 5
3 2 ELECTRICAL CONNECTIONS AND WIRING 5
3 3 POWERING UP5
3 4 LIMITS OF CONNECTED EQUIPMENT 6
4 BASICS OF ELECTRICITY............................................................................................................7
4 1 CHARGE 7
4 2 CURRENT 7
4 3 VOLTAGE 8
4 4 RESISTANCE 8
4 5 POWER 9
4 6 WORK/ENERGY 9
4 7 CONSERVATION OF ENERGY 9
4 8 ABOUT UNITS 10
5 GETTING STARTED.....................................................................................................................11
5 1 MAKING CONNECTIONS 11
5 2 USING AUXILIARY POWER 11
5 3 POWER UP CHECKLIST 12
5 4 APPLYING POWER 12
5.4.1 Applying Power, Examples...................................................................................................12
5.4.2 Applying Power, Problems...................................................................................................12
6 INFORMATION DISPLAY...........................................................................................................13
6 1 STARTUP SCREEN 13
6 2 MEASUREMENT SCREEN 13
6.2.1 (Current) Amps A, Pea Amps Ap........................................................................................13
6.2.2 (Voltage) Volts V, Minimum Volts Vm..................................................................................13
6.2.3 (Energy) Watt-hours Wh.......................................................................................................13
6.2.4 (Charge) Amp-hours Ah........................................................................................................13
6.2.5 (Power) Watts W, Pea Watts Wp........................................................................................14
7 USING WATT'S UP........................................................................................................................15
7 1 WHERE DO YOU CONNECT WATT'S UP15
7 2 MAXIMUM CURRENT CAPABILITIES 15
7 3 USING A WATT METER WITH INDUCTIVE LOADS LIKE MOTORS 15
7 4 RESETTING METER AND CLEARING ACCUMULATED VALUES 16
7 5 CONNECTION DIAGRAMS 16
7 6 INCREASING TRANSIENT VOLTAGE PROTECTION 18
8 BATTERY CHARACTERI ATION............................................................................................20
8.1.1 Battery Charging..................................................................................................................20
8.1.2 Battery Discharging, Efficiency and Health.........................................................................20
8.1.3 Low Voltage Measurement...................................................................................................21
9 SYSTEM CHARACTERI ATION...............................................................................................22
9.1.1 Testing & Troubleshooting Loads........................................................................................22
9.1.2 Capturing Current Pea s, Power Pea s and Voltage Minimums (sags)..............................22
9.1.3 Bac up DC Voltmeter & DC Ammeter.................................................................................23
9.1.4 Calculating Relative Efficiency............................................................................................23
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Table of Contents II
10 WATT'S UP APPLICATIONS.......................................................................................................24
10 1 ON BOARD USE 24
10 2 FLIGHT TIME 24
10 3 BASIC COMPONENT SELECTION 24
10 4 INITIAL TESTING 24
10 5 BALANCING BATTERY PACK CELLS 24
10 6 RECEIVER AND SERVO TESTING 25
11 CARE................................................................................................................................................27
11 1 CLEANING 27
11 2 STORAGE 27
12 TROUBLESHOOTING..................................................................................................................28
13 SUPPORT.........................................................................................................................................30
14 WARRANTY....................................................................................................................................31
14 1 ONE YEAR LIMITED WARRANTY 31
14 2 LIMITS AND EXCLUSIONS 31
14 3 LIMITATION OF LIABILITY 31
14 4 ENTIRE WARRANTY 31
14 5 PROCEDURE FOR WARRANTY CLAIMS AND RETURN AUTHORIZATION 32
15 MEASUREMENT LOG..................................................................................................................33
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Introduction 3
1 INTRODUCTION
Thank you for purchasing the Watt's Up or Doc Wattson power analyzer We are confident
you will find it to be an indispensable addition to the tools you use to make your hobby
more enjoyable
While emphasizing RC modeling applications, this manual applies to the myriad
applications to which the Watt's Up or Doc Wattson meters can be applied While the
Watt's Up model will be referred to, the Doc Wattson is the same with the exception of
some the parameter ranges covered
Your Watt's Up watt meter and power analyzer is an easy-to-use precision instrument for
measuring and calculating the electrical parameters the hobbyist of electronic devices
needs to get the most from their projects
1.1 What it Does
Watt's Up measures current, voltage and time and from those measurements calculates
peak current (Amps), peak power (Watts), minimum voltage (Volts), power (Watts),
energy (Watt-hours) and charge (Amp-hours) values for you, in real-time, for the circuit in
which you connect it
1.2 Benefits
With the advent of electric power for models the hobbyist can now investigate and tune the
performance of their model in ways not possible with the traditional internal combustion
engines With Watt's Up it is now easy to determine things like:
Flight time
Current through an ESC and motor
ESC, BEC and motor efficiencies
Charge put into and removed from a battery and the performance of battery
chargers
Battery health
Presence of peak currents that can damage components
Presence of voltage sags that cause components to operate out of specification
Why power is lost during acrobatics or extreme conditions
Effect of gearing and propeller size and shape on power consumption and battery
currents
Effects of modifications, age and damage on many electrical system components
Clever RC hobbyists will, no doubt, discover new applications to further improve electric
model performance
With Watt's Up you can stop wondering what’s going on with your electric model and get
answers that allow you to apply science to your hobby The precise measurements you
collect will help you fine tune your model to get all the performance that you paid for
We know you are anxious to start using your Watt's Up and ask that you review this
manual first to get the most out of its capabilities and inform you of relevant safety
issues.
Enjoy learning Watt's Up!
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Features and Specifications 4
2 FEATURES AND SPECIFICATIONS
2.1 Features
Measures energy (Wh), charge (Ah), power (W), current (A) and voltage (V)
Connector to use an optional receiver battery for measurement down to 0 V
Accurate & precise – 0 01 A current and 0 01 V voltage resolutions
Measures peak Amps, peak Watts (except for Doc Wattson) and voltage
minimum (sag)
Rugged – handles 50 A continuous and 100 A peak at 60 V
14 ga , super fine stranded, high temperature, silicone rubber insulated wire
Small & light with a tough plastic case available in several colors
Acts like a wire so doesn't affect model's performance Precision Alu-Chrom
current sensing resistor, with only 0 001 Ohms resistance and circuitry that draws only 7 mA
Uses DSP to increase ADC resolution and differential measurement amplifiers to
increase noise immunity
Factory calibration stores constants in EEPROM to compensate for component
tolerances
Powerful, 8 MIPS micro-controller
Made in USA to ISO 9001:2000 quality standards
One-year warranty and complete user manual
2.2 Specifications Tables
Table 1 Electrical Measurement Ranges
Parameter Range Resolution Notes
Voltage 0* - 60 V 0 01 V *0 V min w/ auxiliary power
E g a receiver battery Else 4 0
V
Current 0 – 100 A peak 0 01 A 50 A continuous
Power 0 - 6554 W 0 1 W
Charge 0 - 65 Ah 0 001 Ah 0 – 6554 Ah for Doc Wattson
0 1Ah resolution
Energy 0 - 6554 Wh 0 1 Wh 0 – 655 Kwh for Doc Wattson
0 01KWh resolution
Table 2 Miscellaneous Specifications
Parameter Value Notes
Measurement Update Period 400 mS 650 mS for Doc
Wattson
Signal Sampling Rate ???? samples/s
Data Queue Sequence
time
2 seconds
In Circuit Resistance 0 001 Ohms
Operation Current 7 mA
Auxiliary Power Voltage 4 0 V - 60 V e g from a receiver
battery
Dimensions 2 8" L x 1 7" W x 0 83" D
Weight 2 3 oz 1 7 oz without case
Display Screen 16 character x 2 row STN
LCD
Nominal Operating
Conditions
0 - 50 C ambient
temperature, non
condensing humidity
Maximum
temperature must be
reduced at
maximum current
rating
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Safety Precautions 5
3 SAFETY PRECAUTIONS
CAUTION: High power electrical systems pose dangers independent of devices like the
Watt's Up and it is the user's responsibility to be familiar with these dangers and take any
necessary action to ensure safe use Shorting a rechargeable battery or a Watt's Up
connected to a rechargeable battery or battery charger can supply huge currents and have
serious consequences including explosions, causing fire, damage to equipment and
personal injury
Please carefully read the entire SAFTY PRECAUTIONS section to ensure safe
product use.
3.1 Safe Operation Limitations
The Watt's Up is designed to be safe to use when operated within the parameter limits it
was designed for Typical applications are well within these limits, but it is the user's
responsibility to be familiar with the Watt's Up specifications and ensure the unit is
operated within its limits
Table 3 Safe Operating Limits (Do Not Exceed)
Parameter Operating Range Notes
Voltage 0 V - 60 V
Current 0 - 100 A intermittent
50 A continuous
Assumes device's wires are
in free air and attached to
connections at or below
temperature of 35 C
(95 F) with adequate air
flow 100 A operation time
depends on ambient
temperature and wiring
temperature
Nominal
Operating
Conditions
0 - 50 C ambient air
temperature, non condensing
humidity
Maximum temperature must
be reduced at maximum
current rating
CAUTION: Exceeding these limits may permanently damage the Watt's Up and may
cause personal injury and may cause fire
3.2 Electrical Connections and Wiring
There are risks associated with the potentially high currents measured by the Watt's Up
These include, but are not limited to, fire, burns and personal injury The user must be
familiar with the relevant methods, procedures and connection components before using
or making any connection to the It is suggested that any connectors and wires chosen for
use be appropriately sized and rated for the intended application and attached in the
manner recommended by their respective manufacturers
CAUTION: Poor connections and reckless wire handling in electrical systems may have
serious consequences including personal injury, fire and property damage
Intermittent and loose connections can cause component damage!
3.3 Powering Up
Verify there are no exposed wires or connectors at risk for a short circuit before
connecting a battery or power source to the Watt's Up
The Red “SOURCE” and “LOAD” leads of the Watt's Up are connected to each other
and the Black leads are essentially so This means the "other" side is electrically "hot"
when a battery or other power source is connected to either side
CAUTION: Shorting a rechargeable battery or a Watt's Up connected to a rechargeable
battery or battery charger can supply huge currents and have serious consequences
including explosions, causing fire, damage to equipment and personal injury
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Safety Precautions 6
3.4 Limits of Connected Equipment
The Watt's Up may have measurement capabilities, operating ratings and electrical signal
handling abilities that exceed those of equipment to which it is connected This means the
Watt's Up may be able to make measurements on a connected component despite that
component being operated outside of its safe operating ratings
CAUTION: It is the user's responsibility to consider the limitations of any equipment
connected to the Watt's Up and not to exceed them since the Watt's Up provides no
protection for those components Examples of possible hazards include, without limitation:
charging or discharging batteries outside their voltage and current ratings, application of
excessive voltage or currents to electronic speed controls (ESC) and motors, application of
currents that cause dangerous heating or voltages that present a shock hazard Other
hazards may exist
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Basics of Electricity 7
4 BASICS OF ELECTRICITY
Understanding the basics of electricity will help you get the most out of your Watt's Up and
electric model With these concepts you can intelligently compare electrical components
and conduct experiments to maximize their performance in your electric modeling hobby
If you are new to electrical propulsion systems you may want to read through this a few
times Experts can skip it
We use the water and plumbing analogies to teach electrical concepts because people often
already have good intuition about water systems
4.1 Charge
It all starts with charge
Charge is the basic unit of electric energy Using the water analogy, charge is the “amount
of water”
Charge (electrons actually) is what gets stored in a rechargeable battery by a battery
charger Like water gets “stored” in an aquarium by a water pump a battery charger stores
charge in a battery
Asking how much charge is in a battery is like asking how much water is in an aquarium
A physicist will tell you that charge is measured in units of Coulombs (C) like water can
be measured in units of gallons It turns out that Amp-hours (Ah) is also a unit of charge
and is more familiar to RC hobbyists We’ll show why later when we discuss current
Charge = Current  Time
Charge can be measured in Amp-Hours by:
Amp-hours = Average Amps  hours of duration
4.2 Current
Current is measured as an amount of something flowing per unit of time
With electricity, the “something” flowing in a wire is charge, which is measured in
“Coulombs”
A Coulomb per second of electric charge current has a special name It is called an
Ampere (abbreviated Amps or just A) A gallon per second of water flow doesn’t have a
special name It’s just a gal/s
So 20 Amperes or Amps flowing into a motor means it has a current of 20 Coulombs of
charge flowing per second
Now we can explain why Amp-Hours is a measure of charge
An hour is 60  60 = 3600 seconds So an Amp-hour (meaning Amps times
hours)
= Ampere  Hour
And substituting the definition of an Ampere and of an hour this becomes
= (Coulomb/Second)  3600 Seconds which leaves 3600 Coulombs
Coulombs are charge so there we are -- an Amp-hour (or Ah) is 3600 Coulombs
of charge
It is common in RC modeling to discuss charge in units of mAh The m is an abbreviation
for the Greek “milli” which means “thousandth” of something So 1 mAh is 1/1000 of an
Ah Conversely, 2 Ah is the same as 2000 mAh
Here are some examples showing the important relationships between current, time and
charge
1) Charging
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Basics of Electricity 8
If you pump 1 gal/h of water into an aquarium for five hours it will contain 1
gal/h  5 h = 5 gallons Similarly a battery charging at 1500 mA for one hour
will contain 1 5 Amp  one hour = 1 5 Ah of charge Since we learned above
that there are 3600 Coulombs per Ah, the physicist would say the battery
contains 1 5 Ah  3600 C/Ah = 5400 Coulombs of charge Amp-hr versus C
They are different ways of saying the same thing
2) Discharging
If you know a battery and an aquarium are both “full” you just read their
“capacity” (volume) specification to find the stored “charge ” The aquarium
says 20 gallons and the battery says 2000 mAh The aquarium would take 4
hours to empty at a “current” of 5 gal/h and the battery would take 1 hour to
empty at a current of 2000 mA
4.3 Voltage
Something forces current to flow in a wire That something is called voltage and is
measured in Volts (abbreviated V) The pressure your hand feels pushing water out of a
pipe is the force analogous to voltage
You can’t get a current without a voltage The two are related by the concept of resistance
4.4 Resistance
Resistance is measured in Ohms (abbreviated with the Greek symbol Omega ) It is the
property that limits the current, which flows in a wire for a given voltage applied across the
wire
The very important “Ohm’s Law” summarizes this relationship
Amps = Volts  Ohms
It says the amount of current depends on the voltage applied divided by the amount of
resistance Push harder for a given amount of resistance and you get more flow
Reducing the diameter of a water pipe increases its resistance and therefore reduces the
water flowing from it for a given pressure (voltage) Similarly doubling the resistance of a
wire halves the current flowing through it for a given voltage across it
A useful thing to remember is that 1 Volt divided by 1 Ohm = 1 Amp
It says that One Amp of current will flow in wire having a resistance of one Ohm if one
Volt of voltage is applied across it
So given relatively fixed battery voltages, you need low resistance wires to allow high
currents
Resistance is a general term for a rather complex phenomenon There are different kinds of
resistance For our purposes we will mean Direct Current or DC resistance Alternating
Current or AC resistance is beyond the scope of this tutorial and is not widely discussed in
RC electrical systems
Here’s an example problem using resistance
How much voltage drop is there to a motor drawing 50 Amps if the motor is one
foot from the battery? Assume14 Ga wire has a resistance of approximately
0 0025 Ohms per foot
So we have two feet of wire total with 50 Amps flowing through them Ohms
law tells us that to get 50 Amps through a wire of 2  0 0025 Ohms requires:
Volts = Amps  Ohms, = 50  (2  0 0025) = 0 25 V
So those wires use up 0 25 V in battery voltage Our motor would receive 7 15
Volts from a 7 4 Volt battery Apparently, this motor consumes exactly 50
Amps at exactly 7 15 V
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Basics of Electricity 9
4.5 Power
Power is measured in units of Watts
A key concept:
Power is the rate at which work is done or energy is expended and not the
amount of work done
Or:
Power = energy  time
The power being delivered or used (in Watts) is measured by the current (in Amps)
multiplied by the voltage (in Volts) of the system being measured I E
Watts = Amps  Volts
A battery has a fixed energy capacity or amount of work it can do The rate at which it does
that work or dumps that energy is its power output and that power output can be varied by
the time over which the work is done
For example, the work or energy a battery and motor do to roll an electric car up a 30 foot
hill is the same whether it takes a minute or an hour to do so The power, however, is 60
times greater in the second case!
Using the water analogy, you might fill a 10,000-gallon water tank (representing a fixed
amount of work/energy to be done) in two days with a small electric water pump It would
take a pump attached to a “very powerful” V8 gas engine with a supercharger to fill it in
five minutes Both need the same energy, but require very different powers The difference
is the time the effort takes
4.6 Work/Energy
From a physics point of view, work and energy describe the same thing The word chosen
at a particular time depends on the point of view being emphasized by an author
Hopefully, this will become clear as you read on
People often, incorrectly, mix the concepts of power and energy/work as though they are
the same They are different, but related by time Understanding the difference is very
important toward an understanding of propulsion system performance
Voltage does work to move charge The battery charger worked to push charge against the
battery’s voltage into the battery That work is stored as charge in the battery Discharging
the battery does work on whatever is using the charge
This work or energy is measured in Watt-hours by measuring the power (in Watts)
expended over some time duration (in hours)
Watt-hours = Watts (averaged)  hours
This is how much work the electricity has done
The energy stored in a battery depends on the product of charge and voltage I E
Energy (Wh) = voltage (V)  charge (Ah)
So while a 7 4 V and 14 8 V battery pack may both have the same charge of 2000 mAh, the
14 8 V pack has twice the energy and capacity to do work
4.7 Conservation of Energy
This is a very important physics concept that will help you evaluate electric model power
systems
Simply stated, conservation of energy means that energy isn't ever lost; rather it has gone
someplace "else "
Energy has many forms, Heat, Kinetic, Potential and Chemical being the most relevant to
RC
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Basics of Electricity 10
Two examples will help
1) If you discharge a battery pack into light bulbs the energy stored in the battery's
chemistry was converted to heat in the battery's chemical reaction the wiring and the light
bulb filaments
2) In an electric motor powered plane, energy from the battery converts to heat energy in
wires, connectors, the electronic components in the Electronic Speed Control, the wires in
the motor armature, the brushes, the motor bearings and lubricant and the air the prop and
plane fly through AND to potential energy that has been stored by the height the plane's
mass is above the ground AND to inetic energy stored in the speed of the plane's mass
If you measured all the heat generated and other stored energies, it would equal that
previously stored in the battery That's the conservation
Inefficiency in a process like this means some energy went someplace you didn't want it to
like the wires, bearings, ESC and brushes You wanted it all delivered to the prop
In battery charging, energy from the charger is delivered as a current into a battery where it
is converted to a charge stored in the battery's chemistry In a perfect rechargeable battery
no energy would go anyplace else In reality it does, like to heat, so battery charging is not
100 % efficient
What you can learn from all of this is that your options for an electric powered model's
capabilities must consider all the places energy will be used
Learning some basic things about potential and kinetic energy as well as Newton's second
Law of motion in a simple physics text book will give you powerful tools to evaluate an
electric model capabilities
4.8 About Units
Small amounts of current and voltage are usually measured in milliamps or millivolts
where “milli” is a Greek abbreviation meaning “one thousandth of ” For example, 10 mA
means ten – one thousandths of one Amp, which is written as 0 01 Amps 1000 mA is
another way to write 1 A Similarly, 0 001 V is one thousandth of one volt Milli is a
widely used prefix E g 3000 mAh is another way to write a charge of 3 Ah
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Information Display 11
5 GETTING STARTED
Please be familiar with the contents of the SAFETY PRECAUTIONS section before
continuing.
5.1 Making Connections
Watt's Up is supplied without connectors so you can use whatever kind you prefer
Always connect and disconnect power at the meter FIRST on whichever of the LOAD
or SOURCE sides that has the highest electrical inductance. This is usually at the
LOAD. Long wire runs, motors, generators, etc can have considerable inductance
If you attach connectors to the SOURCE and LOAD leads that mate with those you use on
your models it will be easier to do testing with your Watt's Up However, it is strongly
recommended that you only use female connectors on batteries and other power sources to
prevent connectors and bare metal contacts from shorting together
For example, with female (socket) connectors on your battery you will want male (plug)
connectors on the Watt's Up SOURCE leads and female connectors on the Watt's Up
LOAD leads With this configuration, the Watt's Up can be inserted, like jumper cables,
between the battery and a load such as a ESC with Motor
The user is responsible for selecting connectors rated to handle the current and voltage
expected in the user’s application and to follow the instructions provided with the
connectors to ensure best results
Only qualified individuals should assemble any high current connections
The Red SOURCE wire goes to Positive (Plus +) battery or other device terminals and
black to Negative (Minus -)
Warning: Loose and intermittent connections can cause component damage!
5.2 Using Auxiliary Power
By connecting a receiver battery pack (of at least 4 0 V) or other power source to the 3-pin
connector on the SOURCE side, the Watt's Up can measure down to 0 V This makes it
possible to measure the characteristics of a single battery cell
The 3-pin connector’s socket will accept a Futaba J type, JR or HiTec type servo plug
connector A suitable connector with wires attached is available for purchase from our
website.
Pin 1 is Negative (0 Volts), pin 2 (middle pin) is Positive Pin 1 is the pin farthest from the
Watt's Up SOURCE wires Pin 3, on meter versions 2 1 and above, is for reset of
accumulated readings See below for description of reset operation
When using Auxiliary power, you may see small measurement values when the SOURCE
and LOAD leads have nothing connected or are shorted together It is neither unusual nor a
problem for there to be small values displayed in this situation This will not affect
performance when making real measurements
The Watt's Up has been optimized to provide highest performance for real measurements
of connected power systems and loads, but with all leads unconnected may produce
erroneous readings With real connections, accurate readings will be produced Note that
shorting the SOURCE leads together and/or the LOAD leads together may show a very
small voltage (e g 0 01 Volts) These small “shorted lead” voltages are well within
specification and don't affect the accuracy of real measurements
Caution: Never short leads for testing with a power source connected to either set of
leads!
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Information Display 12
5.3 Power Up Checklist
We recommend you always go through this checklist before applying power to the Watt's
Up
Always verify there are no exposed wires or bare connectors that can short circuit
prior to connecting a battery or power source to the Watt's Up
Carefully inspect wire and connector insulation for damage or bare spots that can
short Properly insulate any such areas with electrical tape or shrink tubing
While a load connection is not required, ensuring that the LOAD wires are safely
routed is important to prevent shorts Capping unused connectors with a fully insulated mating
connector as a "cap" is a useful trick E g capping a female connector with an insulated male
connector
CAUTION: Verify correct connection polarities before applying power or damage
may result!
5.4 Applying Power
The Watt's Up requires a power source providing a minimum of 4 0 V to operate This can
come from a power source (battery or charger) on the LOAD or SOURCE side or from the
auxiliary 3-pin SOURCE power input connector
If you connect an auxiliary power source of 4 0 V or more (e g small receiver battery
pack), the Watt's Up operates independently of power sources on the LOAD or SOURCE
leads This allows measurements down to 0V, e g for measuring a single cell main pack
Note that, for example, a standard 9 V alkaline battery can be wired to an auxiliary
connector and cable to be used as an auxiliary battery if desired
5.4.1 Applying Power, Examples
Use at least a four cell NiCd or NiMH battery pack or a two cell Li-Poly battery
pack on the SOURCE side to provide the minimum 4 0 V Connect a load on the LOAD side E g
an ESC and a MOTOR
Connect an Auxiliary power source to the 3-pin SOURCE power input connector
and a single Li-Poly cell to the SOURCE side and an ESC and motor to the LOAD side
5.4.2 Applying Power, Problems
When you apply power as described, the Watt's Up display will show the "Startup Screen"
and then begin measurements
CAUTION: if the Startup Screen does not appear, immediately remove the power sources
and refer to the troubleshooting section of this document
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Information Display 13
6 INFORMATION DISPLAY
6.1 Startup Screen
Each time power is applied to the Watt's Up SOURCE leads, a startup screen with
firmware revision number is briefly displayed, and then measurement begins
Startup Screen
RCE v2.0
6.2 Measurement Screen
The measurement screen is displayed after the startup screen Amps, Volts and Watts are
continuously displayed All other measured values are presented sequentially, every 2
seconds, in the "Data-Queue®" (DQ) position of the display. All data values are
identified by their units (e g Ah, Wh, Ap, Vm, Wp) All measurement screen values are
updated every 400 mS Note that the Amps, Volts and Watts values are continuously
displayed.
The Measurement Screen layout: Amps, Volts, Watts and the "Data Queue" *
100.00A 10.00V The "Data Queue" shows Ah, Wh,
Ap, Vm, Wp in sequence
Data Queue 1000.0W
* Note: the Doc Wattson screen has Volts and Amps in the same column.
6.2.1 (Current) Amps A, Peak Amps Ap
The Amps value displayed is the average current flowing through the Watt's Up's black
wire over the last screen update interval The displayed Peak Amps value (Ap) is the
maximum current drawn on the LOAD side, since the startup screen ended Watt's Up
circuit operation draws a slight amount of current (7 mA) from the SOURCE side Being
hundreds of times less current than is drawn by typical loads, this slight additional current
can be ignored and the SOURCE’s current be considered equal to the LOAD’s current for
most practical purposes Amps values are measured on the LOAD side Currents over 50
Amps should be measured for reduced time due to wire heating
6.2.2 (Voltage) Volts V, Minimum Volts Vm
The Volts value displayed is the average voltage over the last screen update interval The
displayed Minimum Volts value (Vm) is the minimum voltage (or “sag”) measured on the
SOURCE side, since the startup screen ended The Volts value is measured on the
SOURCE side
6.2.3 (Energy) Watt-hours Wh
The value displayed is the total energy delivered to the LOAD in Watt-hours since power
was applied to the Watt's Up It is measured on the LOAD side For accurate results, be
careful not to interrupt the SOURCE connection to the Watt's Up during an energy
measurement Doc Wattson reports in KWh which is 1000 Wh
6.2.4 (Charge) Amp-hours Ah
The value displayed is the total charge in Amp-hours delivered to the LOAD since power
was applied to the Watt's Up It is measured on the LOAD side For accurate results, be
careful not to interrupt the SOURCE connection to the Watt's Up during a charge
measurement
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Information Display 14
6.2.5 (Power) Watts W, Peak Watts Wp
The value displayed is the average power delivered in Watts over the last screen update
interval The displayed Peak Watts value (Wp) is the maximum power drawn on the LOAD
side, since the startup screen ended Watts values are measured on the LOAD side
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Using Watt's Up 15
7 USING WATT'S UP
7.1 Where Do You Connect Watt's Up
You can think of the Watt's Up like a set of jumper wires Connect it in the same way and
you can measure what the jumper wires are connected to Like Jumper wires, the Watt's Up
is essentially a direct connection between correspondingly colored SOURCE and LOAD
wires, i e both the “SOURCE” and “LOAD” leads of the Watt's Up are electrically “hot”
when a battery is connected to either side
Example use #1 -- Testing Loads; Battery on SOURCE side, Electronic Speed
Controller (ESC) and motor on LOAD side With the ESC on, the Watt's Up shows the
current into the motor, voltage and power at the battery and accumulates the Ah and
Wh while the motor is running
Example use #2 -- Battery Charging; with a battery charger on the SOURCE side and
battery pack on the LOAD side (using gender changing jumpers), the Watt's Up shows
the charging current into the battery, the voltage and charging power at the battery and
accumulates the charge (Ah) and energy (Wh) into the battery
7.2 Maximum Current Capabilities
Current flowing through Watt's Up and its supplied wires generates heat due to the
resistances of the wires and of the precision internal current shunt used for current
measurements Though very low ( ~ 0 004 Ohms in 14 gage wires and 0 001 Ohms in
shunt), these resistances are finite and at high currents the heat generated becomes
noticeable This is because heat is created with the "square" of the current I E :
heating power (W) = current2 (A)  resistance (Ohms)
So doubling the current increases the heat produced four times
At 75 Amps, approximately 28 Watts of heat is produced – mostly in the Watt's Up's wires
This doesn't only happen with Watt's Up All wiring, connectors, etc have resistance
subject to the same resistance based heating
The high current handing capabilities of Watt's Up will be maximized when the Watt's Up's
SOURCE and LOAD wires are kept short and cool Cut the wires as short as is convenient
for high current operation A fan blowing over the wires will help their cooling At
moderate currents there is little heating Using a "three-wire" connection will also lower
heat generation. Please see our Internet website connection diagrams and FAQ for more
information on connections
7.3 Using A Watt Meter with Inductive Loads Like Motors
Loose connections and long wires on circuits switching high currents can damage electrical
components The problems can be largely eliminated by ensuring that connections are
secure/not intermittent (e g not just twisted together) and to a lesser degree by keeping
wire lengths short and by twisting wire pairs together to reduce their inductance Here's a
little more about why this all happens
Wires exhibit a property called inductance Inductance is an indication of the amount of
energy stored in a wire's magnetic field due to the flow of current
If you interrupt the current flow, say with a switch or pulling apart a connector, the
magnetic field collapses and induces a voltage in the wire to try and oppose the drop in
current Depending on the specifics of the wire, current and materials near the wire (like
iron) the induced voltage can be quite high In fact, it can give you a mild shock and
damage electrical components still connected to the wire by generating voltages that
exceed their ratings. This is one of the reasons capacitors and diodes are needed on brushed
motors in addition to reducing RF noise
Always disconnect the meter from the highest inductance wiring first. Usually this is
on the LOAD side.
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Using Watt's Up 16
7.4 Resetting Meter and Clearing Accumulated Values
All accumulated readings including Ah, Wh, peak current, etc can be reset to zero in one
of two ways
1 Completely remove all voltage from the Source's Red AND the Auxiliary Connector's
Pin 2 or,
2 On meter versions 2 1 and above, briefly (e g a thousandth of a second) connecting the
Auxiliary Connector's pin 3 to zero Volts E g pin 1 or the meter's black wire Meter
versions prior to version 2 1 do not have the Pin 3 reset capability
Note that the meter will be held reset and not function if the reset signal (pin 3) is
continuously connected.
Pin 1 is the pin farthest from the Watt's Up SOURCE wires Pin 3 is nearest the SOURCE
wires
Pin 3 has a 3 3K Ohms input impedance
See diagrams below to understand the reset function connections.
7.5 Connection Diagrams
The following diagrams show example connections between the Watt's Up and various
Sources and Loads using a "four-wire" connection
A "three-wire" connection only connects the meter's red (plus) lead at the LOAD or the
SOURCE, but not both A separate wire must be present to make the SOURCE to LOAD
(e g battery to speed control) connection "around" the meter The advantage of the three-
wire connection is that only the meter's black wires must carry current and therefore be
heavy and that the heat generated in the meter is reduced since there is only low current in
the red voltage sense wire to the meter
An example three-wire hookup is shown in the diagram for reset and transient
voltage protection further on in this document.
Generally, the three-wire connection is the highest performance and is recommended The
four-wire "jumper cable" approach can be easier to understand and may simplify connector
usage
Please see our Internet website connection diagrams and FAQ for additional information on
making connections
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc

Using Watt's Up 17
The following are some example four-wire meter connections Many other arrangements
and uses are possible
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc
T e s t i n g L o a d s
( e . g . m o t o r s )
" W a t t ' s U p "
w a t t m e t e r
B a t t e r y
( 4 - 6 0 V ) *
- -
S p e e d
C o n t r o l
- -
M o t o r
( B r u s h e d o r
B r u s h l e s s )
B a t t e r y
C h a r g e r
( 4 - 6 0 V ) *
B a t t e r y
-
-
-
SOURCE
LOAD
" W a t t ' s U p "
w a t t m e t e r
- -
SOURCE
LOAD
p l u g - p l u g
j u m p e r w i r e s
" W a t t ' s U p "
w a t t m e t e r
B a t t e r y
( 0 - 6 0 V )
- -
D i s c h a r g e
L o a d
- -
SOURCE
LOAD
B a t t e r y C h a r g i n g
B a t t e r y D i s c h a r g i n g
L o a d s
P o w e r S o u r c e s
L e g e n d
P l u g c o n n e c t o r
S o c k e t c o n n e c t o r
A u x i l i a r y
B a t t e r y
( 4 - 6 0 V )
-
S h o w s a u x i l i a r y b a t t e r y c o n n e c t e d t o
a l l o w m e a s u r e m e n t d o w n t o 0 v o l t s
* 0 V i f u s i n g a u x i l i a r y b a t t e r y .
" W a t t ' s U p "
w a t t m e t e r
R e c e i v e r
B a t t e r y
( e . g . 4 . 8 V )
- -
-
R e c e i v e r
-
SOURCE
LOAD
R e c e i v e r & S e r v o
T e s t i n g
A u x i l i a r y
B a t t e r y
( 4 - 6 0 V )
-
.
.
.
S e r v o n
S e r v o 1
y o u r a d a p t e r /
j u m p e r w i r e s
v 1 . 1

Using Watt's Up 18
The following are some example three-wire meter connections Many other arrangements and
uses are possible
L o a d s
P o w e r S o u r c e s
L e g e n d
P l u g c o n n e c t o r
S o c k e t c o n n e c t o r
" T h r e e - W i r e " H o o k u p f o r
R e m o t e L o a d M e a s u r e m e n t
w i t h A u x i l i a r y P o w e r I n p u t
- -
SOURCE
LOAD
D C
I n v e r t e r
-
A C L o a d
" W a t t ' s U p " / D o c W a t t s o n
D C P o w e r A n a l y z e r
B a t t e r y
-
A u x i l i a r y
P o w e r
S h o w s o p t i o n a l a u x i l i a r y b a t t e r y c o n n e c t e d t o
a l l o w m e a s u r e m e n t b e l o w 4 v o l t s .
R e s e t s i g n a l c a n b e u s e d i n d e p e n d e n t l y o f
A u x i l i a r y p o w e r .
" T h r e e - W i r e " H o o k u p f o r
R e m o t e L o a d M e a s u r e m e n t
- -
SOURCE
LOAD
N o c o n n e c t i o n
P l u s c o n n e c t i o n t o
m e t e r c a n u s e l i g h t
g a g e w i r e a s o n l y
c a r r i e s c u r r e n t t o
p o w e r m e t e r
D C
I n v e r t e r
-
A C L o a d
" W a t t ' s U p " / D o c W a t t s o n
D C P o w e r A n a l y z e r
B a t t e r y
-
N e g a t i v e L e a d
C u r r e n t F l o w
O p t i o n a l , n o r m a l l y
c l o s e d , p u s h b u t t o n
s w i t c h t o r e s e t
m e t e r r e a d i n g s b y
r e m o v i n g p o w e r
© c o p y r i g h t 2 0 0 4 - 2 0 0 7 R C E l e c t r o n i c s , I n c . A l l r i g h t s r e s e r v e d
O p t i o n a l , n o r m a l l y
o p e n , s i n g l e p o l e ,
p u s h b u t t o n s w i t c h t o
r e s e t m e t e r r e a d i n g s
u s i n g t h e r e s e t s i g n a l
X
X
v 1 . 1
-
7.6 Increasing Transient Voltage Protection
The Watt's Up and Doc Wattson meters can be applied in a wide range of measurement
applications, some of which pose an increased risk of damage to the meter This risk is due
to over voltage (from a variety of mechanisms) that exceeds the meter's rating and damages
internal components
Providing sufficient built-in protection to survive any transient condition is both expensive,
can reduce performance and is generally unnecessary
The following are three suggestions for external circuitry you can add to significantly
increase the meter's ability to survive damaging transients These suggestions are
necessarily technical and intended for a technically savvy audience Sorry, but we can not
provide support for the suggestions in this section due to the potential complexities of
application and wide range of customer technical training and ability.
See diagram below to better understand the suggestion connections.
Three Suggestions:
"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual RC Electronics, Inc