Powerware ST-2400S User Manual

Model ST-2400S

Horsepower Computer System

User Manual

In the USA:

Star Test Dynamometer, Inc.

712 Thistlewood Court

Normal, IL 61761

Phone: [phone]

In Mexico, Central & South America:

Negociaciones Fuentes S.A. DE CV

Av. La Luz 4549 Col. Cortijo del Rio

Monterey, N.L. Mexico 64890

Phone: [phone]

Manufacturered by:

Ries Labs, Inc.

2275 Raven Road

Farina, IL 62838

Phone: [phone]

eMail: [e-mail]

Table of Contents

Description ---------------------------------------------------------------- 3

Installation ---------------------------------------------------------------- 3

Power Supply --------------------------------------------------------- 4

Operation of the unit from 220-260 VAC 50-60 Hz ----------- 4

Operation ------------------------------------------------------------------ 4

Computer Function Switch ---------------------------------------- 5

System Power LED -------------------------------------------------- 6

Torque Set Switch --------------------------------------------------- 6

Printer/Computer Interface --------------------------------------- 7

Computer Software for the 2400S horsepower computer --- 8

Calibration Software for the 2400S ----------------------- 8

Dyno32 Software ---------------------------------------------- 8

DynoGraph Software ---------------------------------------- 9

Calibration ------------------------------------------------------------- 9

Calibration Procedures ------------------------------------- 10

Calibration Procedure Notes ------------------------------ 11

Torque Calibration Notes --------------------------------- 12

In case of Difficulty ----------------------------------------------------- 14

2

Description:

The function of the Model 2400S Horsepower Computer is to provide the operator with a
continuous digital readout of the RPM, TORQUE, POWER (Horsepower or Kilowatts)
and percentage of Torque Rise ( % TORQUE RISE) when properly attached to a
compatible dynamometer.

The RPM readout shows the operator the rotation speed (rotations per minute) of the
power shaft of the dynamometer. The RPM is measured by a pickup and gear
combination that is mounted on the dynamometer and coupled to the power shaft of the
dynamometer.

The TORQUE readout shows the operator the torque (Foot-Pounds or Newton-Meters)
being produced by the prime mover being tested. This is the same as the torque applied
to the dynamometer by the power source (motor, engine, drive wheels, etc.). The torque
is measured by a load cell that is mounted on the dynamometer.

The POWER readout shows the operator the amount of power being produced by the
prime mover and applied to the dynamometer. This is the same as the power being
absorbed by the dynamometer. It is computed by the Horsepower Computer using the
RPM and Torque measurements using the formulae below:

HORSEPOWER = ( RPM * TORQUE (foot-pounds) ) / 5252

KILOWATTS = ( RPM * TORQUE (Newton-Meters)) / 9549

The % Torque Rise (% Torque Load) meter shows the torque as a percentage compared
to a reference torque value. It is used to measure the “lugging ability” of an engine.

The Horsepower Computer has a RS-232 compatible serial interface which can be
connected EITHER to compatible serial printer OR to an external computer system.
When connected to a printer, the system may be used to provide a “hard copy” printout of
measurement results. When connected to an external computer, the system may be used
for printing, storing, graphing, (etc.) the measurements performed by the dynamometer
system (including the dynamometer, horsepower computer, and external computer).

Installation:

The Model 2400S horsepower computer should be installed in a location where the unit is
not exposed to wetness, extremely high temperatures, prolonged direct sunlight, or other

environmental factors that would shorten the life expectancy of the unit

.

3

Power Supply:

The Model 2400S horsepower computer is normally operated from 110 to 125
VAC (60 Hz) using the outlet mounted power supply that is supplied with the
unit. The power consumption of the computer is very low and the unit has a very
high tolerance for power supply variations, so nearly any standard 115 VAC
utility power outlet should power the unit adequately. See (below) information on
a special (optional) “wide-range” power supply which will power the unit
properly when the line voltage is either very low or very high.

The computer may also be operated from a source of 12 to 18 Volts DC such as a
small DC power supply or 12 Volt storage battery. If a storage battery is used, be
sure that it is properly charged. If the battery voltage is low, the POWER LED of
the unit will flash “on” and “off” about once every second – indicating that the
power supply voltage is inadequate to power the unit properly. NOTE: WHEN

OPERATING THE UNIT FROM A BATTERY OR POWER SUPPLY,
THE POLARITY (+/- WIRING) MUST BE CORRECT OR THE UNIT
WILL NOT OPERATE. WIRING A BATTERY OR POWER SUPPLY TO
THE UNIT WITH IMPROPER POLARITY MAY RESULT IN DAMAGE
TO THE UNIT.

Operation of the unit from a 110 to 250 VAC 50 to 60 Hz power source

A special “universal input” power supply is available (as an option) which will
allow the unit to be operated from a wide range of AC power sources – both
domestic and international.

This power supply has a detachable power cable which may be easily replaced
with a power cable which matches the local power system.

This power supply is also very useful when operating the unit from power
sources which may be lower than standard and/or slightly erratic. This
power supply will result in proper operation when the AC power source is a
low as about 90 Volts AC.

Operation:

The horsepower computer normally operates with a two second measurement
cycle. It can optionally be factory programmed for a one second measurement
cycle. During the measurement cycle, the RPM of the dynamometer shaft is
measured along with the torque sensed by the dynamometer load cell. At the end
of each measurement cycle, the RPM and TORQUE values (averaged over the
measurement interval) are displayed and the POWER and % TORQUE RISE

4

values are computed and displayed. This process is repeated continuously while
the unit is in operation.

Computer Function Switch:

The computer function switch is used to turn the system power ON/OFF
and to control the functional operation of the horsepower computer. The
function switch has four positions ( “OFF”, “ZERO”, “CHECK”, and
“RUN”).

In the “OFF” position, the power to the horsepower computer (and the
load cell, etc.) is turned “OFF”. The power is turned “ON” in the other
three positions of the computer function switch.

The horsepower computer has two user controllable self test modes
(“ZERO” and “CHECK”). These can be used to test much of the
horsepower computer’s internal circuits for proper operation. In the
ZERO position, internal test signals are fed into the RPM and TORQUE
measurement circuits. In the ZERO position of the function switch, these
signals should result in readings of zero on all four displays. If the reading
of any display remains substantially different from zero (more than +/- 1
or 2 counts) when in the zero mode, some type of malfunction of the unit
is indicated.

The second user controllable test mode is the CHECK mode. In this
mode, internal test signals are fed to the RPM and TORQUE measuring
circuits to simulate normal operation of the unit at about 37.5 % of full
scale torque. The actual readings shown on the displays of the unit depend
on internal factory set optional settings – principally the full scale torque
value (which corresponds to the size of the load cell being used with the
unit). The RPM display should read about 4000 RPM (+/- 1 or 2 counts)
on all units. The Torque display should read about 37.5 % of the load cell
rating. Refer to the tables below for the proper readings of the Torque and
Power displays for your unit. The Power reading should agree with the
power you compute from the actual RPM and TORQUE readings (within
+/- 1 or 2 counts) using the above formulae for the horsepower or
kilowatts.

Load Cell Rating (Ft.-Lbs.) Torque (Ft.-Lbs.) Power (HP)
100 37.50 28.56
200 75.00 57.10
500 187.5 142.8
1,000 375.0 285.6
2,000 750.0 571.0
5,000 1875 1428

5

10,000 3750 2856

CHECK readings using Ft.-Lbs. & Horsepower

6

Load Cell Rating (Ft.-Lbs.) Torque (N-M) Power (KW)
100 (135.5 N-M) 50.84 21.30
200 (271 N-M) 101.6 42.60
500 (677.5 N-M) 254.2 106.5
1,000 (1355 N-M) 508.4 213.0
2,000 (2710 N-M) 1016 426.0
5,000 (6775 N-M) 2542 1065
10,000 (13550 N-M) 5084 2130

CHECK readings using Newton-Meters and Kilowatts

The ZERO and CHECK positions of the computer function switch
provide quick checks to determine whether the horsepower computer is
operating properly. Proper readings indicate that the major portion of the
computer is working correctly. Note that the Load Cell sensor circuits and
the RPM pickup circuits are NOT tested in the ZERO and CHECK modes.

With the dynamometer at rest and the computer function switch set to
“RUN”, the speed and power displays should show zero (“0”). The torque
display may show some small value --- typically less than +/- 3 Ft.-Lbs (4
N-M). The % torque rise display reading depends on whether or not the
reference torque has been set and if so, to what value – so the reading of
this display should be ignored at this time. See also the section below.

System Power LED:

The system power LED (Light Emitting Diode) is located on the front
panel of the unit, just to the left of the computer function switch.

This green LED indicates that power is applied to the unit and the unit is
turned “ON”.

If this light is slowly flashing ON and OFF, this indicates that the power
supplied to the unit is inadequate (voltage is too low or too un-steady) and
that the readings produced by the unit are likely in-accurate as a result.

Torque Set Switch:

The reference torque set switch is located on the front panel of the unit –
just to the right of the computer function switch. Your unit may (as an
option) be equipped with a remote torque set switch. This switch is
located remotely from the horsepower computer but functions the same as
the torque set switch.

7

The torque set switch is used to set the torque reference which is used to
compute the % Torque Rise reading. To set the torque reference, proceed
as follows:

Run the engine at it rated speed, loaded at rated power or torque output.
This represents the 100% torque output condition for the engine.

With the engine running at its rated speed and load, press the Torque Set
switch momentarily. The reference torque value is now set to the rated
engine 100% torque and the % Torque Rise display should now read 100.0
(100%). All future measurements will now display the torque on the %
Torque Rise meter as the percentage of the reference torque value. For
example, if the % torque rise meter reads 75.0, this means that the current
actual torque is 75.0% of the reference (or rated) torque.

Printer / Computer Interface:

The Model 2400S horsepower computer is equipped with a RS-232-C
compatible serial interface. This interface can be used to operate a small
serial printer to make “hard copy” printouts of test results. Alternately,
this interface can be used to connect the horsepower computer to a
Windows type personal computer for calibration setup and so that test
results can be saved, printed using the PC’s printer, etc. The horsepower
computer senses which type of device is connected to the serial interface
(printer or computer) and operates the interface accordingly. It is NOT
possible to connect a serial printer and a personal computer to the
horsepower computer at the same time.

The print rate controls (“Report Rate” and/or “Manual Print”) are used to
select which measurements are printed or sent to the personal computer.
These controls are located on the front panel of the unit, above the
Computer Function switch. Your unit may (optionally) be equipped with
a remote manual print switch – which functions the same as the manual
print switch but which may be located remotely from the horsepower
computer.

The Report Rate switch is used to control the rate at which the unit prints
test results. Various automatic rates are available, from one report every
10 seconds up to one report every thirty minutes. There is also a “manual”
position on this switch. In the manual position, the unit only makes a
printout when the manual print switch is pressed (momentarily).

The manual print switch can be used at all settings of the report rate
switch. It is NOT necessary to set the report rate switch to manual in
order to use the manual print switch (or the optional remote print switch)
to trigger a print report.

8

When the horsepower computer is used with a companion personal
computer, a standard (9 pin) RS-232-C extension cable is used to connect
the two computers together. This extension cable is normally 10 feet long,
but can be up to 50 feet long (and even longer if special “long range” RS­232-C extension cables are used). The print rate and manual print
switches serve to notify the personal computer which measurements are to
be saved (or printed) in much the same way they are used when a printer is
attached to the horsepower computer.

Software for the 2400S horsepower computer:

There are several software programs for the 2400S horsepower computer. These
include:

Calibration Setup Software for the 2400S:

HpcOptionsW32 is software for the 2400S horsepower computer
which is used to prepare the 2400S for calibration. This is done so
that the 2400S will “know” the details of the method you will use
to check the torque calibration of the unit. This “factory setup” is
normally performed on the 2400S by your dealer prior to delivery
of the 2400S to you so won’t have to.

If you change your calibration method or calibration tools, this
program can be used to inform the 2400S of the changes so that
subsequent torque calibrations will be accurate.

If you use a NIST traceable calibration method, this program must
be used periodically (each time the load cell and the 2000S
horsepower computer are sent in to have their NIST calibrations
checked) to inform the 2400S of any changes to the load cell
calibration or the internal 2400S traceable shunt resistor
calibration.

HpcOptionsW32 is compatible with most Windows based
computer systems including Win95, Win98, WinMe, Win2000 and
WinXP.

Data Recording Software for the 2400S (Dyno32):

The Dyno32 software makes it easy to reproduce the 2400S
horsepower displays on the screen of the personal computer for
remote viewing, etc. There are also features for printing and
recording (saving) your dyno measurements. Data printing and

9

Data Recording and Graphing Software for the 2400S:

Calibration:

The calibration of the Model 2400S horsepower computer should be
checked at least once per year – or sooner if any doubts or questions arise
as to whether the readings produced by the unit are within the accuracy
specifications of the unit.

The Model 2400S should also have its calibration checked if any of the
following events occur:

1.) The instrument has been dropped or otherwise mistreated.

recording can be controlled from the 2400S horsepower computer
and / or using the personal computer’s keyboard or mouse.

Recorded data can be printed on the PC’s printer and / or can be
easily “imported” into Microsoft Excel (or other analysis
programs) for further operations such as graphing, etc.

Dyno32 is compatible with most Windows based computer
systems including Win95, Win98, WinMe, Win2000 and WinXP.

DynoGraph software combines most of the features of Dyno32
with a “built-in” storage, printing, and graphing capability to
streamline the computerization of your dynamometer system.

The DynoGraph software integrates the important Dyno data
collection, display, storage, and printing functions into one easy to
use program that helps you to maintain complete records of the
measurements you take using your dynamometer system. It also
creates professional reports of your measurements including
graphs of the important parameters such as Torque vs. RPM,
Power vs. RPM, etc

Up to 100 measurement “points” can be included in one
DynoGraph document. There is provision to include your
company info (name, address, etc.) along with the important
information about the device being measured (customer info,
machine info, date and time of the measurements, etc.)

DynoGraph software is compatible with most Windows computer
systems including Win95, Win98, WinMe, Win2000 and WinXP.

10

2.) The instrument has been moved (re-installed) from one dynamometer

to another.

3.) The load cell of the dynamometer has been replaced, overloaded,

dropped or otherwise mistreated.

4.) The power supply to the unit has been repaired or replaced.

5.) Prior to any measurements that require especially high accuracy.

6.) The instrument has been repaired, exchanged or replaced.

IMPORTANT NOTE:

The Model 2400S is a delicate instrument and should be treated accordingly. It
should not be allowed to get wet, be exposed to excessive temperatures, dropped or
subjected to excessive shock or vibration. It should only be used with an approved
power supply.

It contains no user serviceable parts and no attempt should be made to repair or
modify the unit.

If the unit is in need of repair, it should be returned to the dealer or directly to Ries
Labs, Inc. for repair.

When it becomes necessary to check the calibration of the unit, follow the
procedure below.

Calibration Procedure:

The Model 2400S horsepower computer uses quick and easy “push­button” calibration methods and can be calibrated using a variety of
methods. Be sure to use the one that is correct for your dynamometer
system and the calibration tools that are available to you.

Prior to attempting calibration, first verify that the 2400S is operating
correctly using the ZERO and CHECK positions of the computer
function switch. If the 2400S does not pass these checks, there is a
problem with the unit and it should be repaired before any attempt is
made to calibrate the unit.

Calibration of the Model 2400S is a simple, two step process:

1.) Set the ZERO calibration: The dynamometer should not be running

and should be disconnected from the engine, tractor, motor, etc. The
RPM reading should be exactly zero and the TORQUE reading should
be fairly close to zero – especially if the unit has previously been
calibrated to the load cell. If necessary, disconnect the load cell from

11

the torque arm of the dynamometer to insure that there is no force
being applied to the load cell (which would result in an inaccurate zero
calibration). Remove the calibration access cover panel and set the
calibration mode switch to the ZERO position. Also, be sure that
the shunt resistor switch is set to the OFF position. At this time note
that the RPM display of the unit should indicate “1111” and the
POWER display should indicate “0000”. The TORQUE display
indicates the TORQUE and should read near zero. If the torque
indication is excessive (plus or minus), the POWER display will read
“EEEE” – which indicates that the zero offset of the load cell is
excessive and that the ZERO calibration cannot proceed (see
calibration notes below). Otherwise, press and release the ENTER
push-button switch to perform the zero calibration. At this point, the
TORQUE display should indicate zero and the zero calibration
procedure has been completed.

2.) Set the TORQUE SPAN calibration: Apply the CALIBRATION

TORQUE (see calibration torque notes below) to the unit and set the
calibration mode switch to the SPAN position. At this point the
RPM display should indicate “2222”, the POWER display should
indicate “0000”, and the TORQUE display should indicate a value
approximately equal to the CALIBRATION TORQUE. If the
deviation between the torque reading and the calibration torque is
excessive, the POWER display will read “EEEE” – indicating that the
TORQUE SPAN calibration cannot proceed (see calibration notes
below). Otherwise, press and release the ENTER push-button switch
to perform the TORQUE SPAN calibration. Now the TORQUE
display should indicate the value of the CALIBRATION TORQUE
and the torque span calibration has been completed.

3.) Resume normal operation: Set the calibration mode switch back to

the OFF (center) position. This turns off calibration mode and
restores the unit to normal operation. Be sure to return the shunt
resistor switch to the OFF position (if you used it during the torque
span calibration). Replace the calibration access cover panel. The unit
has now been accurately calibrated.

Calibration Procedure Notes:

1. ZERO CALIBRATION cannot proceed. This problem occurs when the ZERO

OFFSET is excessive – too large for the zero offset correction facility of the 2400S to
correct. Check the following:

1.1 Make sure that the load cell is properly connected to the 2400S horsepower

computer. Inspect the cable for damage, especially at the load cell end and the
connector end. Make sure the connector is securely fastened to the 2400S torque
sensor connector.

1.2 Make sure that the load has been completely removed from the load cell. “Rock”

the drive shaft of the dynamometer CW and CCW slightly (applying a small

12

positive and negative torque to the unit) and verify that the torque reading returns
closely to the same value. A failure here indicates a likely problem with the
dynamometer. Have the dynamometer checked by your dealer or dyno service
person.

1.3 Make sure that the load has been completely removed from the load cell.

Disconnect the load cell from the torque arm of the dynamometer by removing
the coupling fastener. If this does not correct the excessive zero offset a likely
defective or damaged load cell is indicated. You should have the load cell
checked by your dealer or dyno service person.

1.4 Make sure that the shunt resistor switch is set to the OFF position.

2. TORQUE SPAN CALIBRATION cannot proceed. This problem occurs when the

torque reading is not sufficiently close to that expected from the CALIBRATION
TORQUE value. Check the following:

2.1 Check to be sure that the CALIBRATION TORQUE is the value expected by the
2400S horsepower computer. The expected calibration torque value is normally
programmed into the 2400S by your dealer to match the calibration value and method
you will be using to check and adjust the calibration of your unit. You can check this
by setting the calibration mode switch back to the OFF position while leaving the
CALIBRATION TORQUE applied to the unit. The TORQUE display will now read
the (approximate) torque you have applied. If this value is within about +/- 10% of
the CALIBRATION TORQUE that you have applied, then it is likely that the value
expected by the 2400S for the CALIBRATION TORQUE is different than the value
you are using. Check with your dealer or dyno service person to determine the
calibration torque you should be using or use the 2400S calibration setup software to
re-program the 2400S to expect the calibration torque you are currently using.

2.2 If the TORQUE display does not read (within +/- abut 10%) the torque that you
have applied a possible defective or damaged load cell is indicated and may need to
be repaired or replaced. Have your dealer or dyno service person assist you.

Torque Calibration Notes:

There are several methods which can be used to apply a calibration torque value to the
2400S horsepower computer.

1.) Dead Weight Test Fixture: This method uses a Torque Test Bar (dead weight

test fixture) and one or more calibration weights. The torque test bar is attached
to the torque arm of the dynamometer, being careful to align the position of the
mark on the torque test bar with corresponding mark on the torque arm of the
dynamometer. Then connect the test weight(s) onto the torque test bar at the
indicated position, usually the 4 foot (1.210 meter) position. The torque produced
by the torque test bar must be accurately known, the total weight of the test
weights must be accurately known, and the horizontal distance from the center
line of the dyno to the indicated position must be accurately known. If any of
these three factors is not accurate, then the resulting calibration will not be
accurate –and the result is in-accurate torque and power readings from the

13

dynamometer. The calibration torque produced is equal to the sum of the torque
produced by the Torque Test Bar itself plus the torque produced by the test
weight(s) – which is equal to the total weight of the test weight(s) times the
horizontal distance from the center line of the dyno to the position of the test
weights. For example, assume the torque of the torque test bar itself is 17 Ft.­Lbs., the total weight is 100 Lbs. and the horizontal distance is 4.00 Ft. The
calibration torque value produced by this setup is equal to 417 Ft.-Lbs. ( = 4.00
Ft. * 100 Lbs. + 17 Ft.-Lbs.)

2.) Shunt Resistor: The 2400S horsepower computer has an internal shunt resistor

which can be used to check the torque span calibration. The 2400S can
(optionally) be equipped with a precision shunt resistor which can be used to
perform a NIST (National Institute of Standards and Time) traceable torque
calibration. The “torque” introduced by the shunt resistor depends on the
resistance value of the shunt resistor as well as the properties of the load cell. For
the NIST traceable torque calibration to be accurate, both the shunt resistor value
and the load cell must have NIST traceable calibrations which should be checked
periodically. A 2400S horsepower computer without the precision shunt resistor
is equipped with a 1% precision 45.3 K Ohm shunt resistor (not adequate for
NIST traceable calibrations) which can be used for a quick and fairly accurate
check on the torque calibration and the torque sensor circuits of the 2400S. After
performing the calibration of the unit using the dead weight test fixture calibration
method, remove the dead weight test fixture and set the Shunt Resistor Switch to
ON. The shunt resistor will produce a torque reading that is (roughly) 2/3 of the
full scale torque of the unit (i.e. about 3300 Ft.-Lbs. on a 5000 Ft.-Lbs. full scale
2400S). More precise values are shown in the table below. The reading should
be within +/- 2 or 3 % of the appropriate value from the table below. The
tolerance derives from the +/- 1% tolerance of the 45.3 K Ohm shunt resistor plus
the tolerance of the load cell (likely +/- 1 or 2 %). If the reading is not this close,
you should double check the calibration and your procedure as a likely problem is
indicated. If the reading is within the above limits, record its value. It can be
used later for a quick check on your unit’s calibration as it should be stable over
time and temperature to within +/- 0.25% or better.

Full scale Torque (Ft.-Lbs.) 45.3 K Ohm Shunt Resistor Torque
100 64.14
200 128.3
500 320.7
1,000 641.4
2,000 1283
5,000 3207
10,000 6414

14

In Case of Difficulty:

The following is a troubleshooting guide that will help you to resolve any problems that
may arise.

The Model 2400S Horsepower Computer contains no user serviceable parts. If it needs
to be repaired you may return the unit to your dealer (who can also assist you with other
repair problems such as problem diagnosis, replacement of the load cell, RPM pickup,
other dynamometer repairs, etc.) or directly to:

In the USA:

STAR TEST DYNAMOMETER, INC.

712 THISTLEWOOD COURT

NORMAL, ILLINOIS 61761

PHONE: [phone]

In Mexico, Central & South America:

Negociaciones Fuentes S.A. DE CV

Av. La Luz 4549 Col. Cortijo del Rio

Monterey, N.L. Mexico 64890

Phone: [phone]

You may also return the 2400S Horsepower Computer and its power supply directly to
the manufacturer for repair:

RIES LABS, INC.

2275 RAVEN ROAD

FARINA, ILLINOIS 62838

PHONE: [phone]

E-MAIL: [e-mail]

Be sure to include a written description of the problems you are having with the unit, the
name and phone number of a person to call if we need to discuss your problem with you,
and return shipping instructions. If the unit is out of warranty, please also include a
repair order and information about how you want the repaired unit returned to you. Ries
Labs, Inc. does not open commercial accounts (charge accounts) for repair work. Ries
Labs, Inc. accepts electronic payments (credit card or otherwise) using PayPal. You can
sign up for your PalPal account by visiting
payment via PalPal is FREE, EASY, QUICK and SAFE.

Ries Labs, Inc. does not offer repair services for the other components of your
dynamometer – only 2000S and 2400S horsepower computers, their power supply, and
other items manufactured by Ries Labs, Inc.

http://www.paypal.com/ Sending your

15

The following table is useful for you to determine that cause of any problems that you
might be able to fix yourself.

Problem Possible causes and remedies
No indication on displays.
Power LED is not lit.

Power LED comes ON
and OFF erratically

Power LED flashes ON
and OFF regularly

Unit blows fuses Power supply voltage may be too high. The power supply

RPM display reads zero
all the time, or is erratic

Torque display reads –
EEE or some other value
all the time (or is erratic)

Printer doesn’t work (or
works erratically)

Horsepower or Kilowatt
readings are low or not
correct

RPM readings are
inaccurate

There is likely no power to the unit. Check the power supply
to be sure it is plugged in. Check the fuse on the front panel
of the unit. Replace ONLY with the correct ½ amp fuse. DO
NOT use a slow blow or higher value fuse as this can result
in severe damage to the unit.
Check to be sure the power supply is plugged in securely.
Try another outlet. Make sure the power connector is
fastened tightly to the front of the unit.
Power supply voltage is too low. Check the power supply or
battery. The supply voltage must be at least 12 Volts with
low power supply “ripple” for the unit to operate properly.

voltage should be less than 20 Volts DC or damage to the
unit will occur. Send the 2400S for repairs if the unit blows
fuses when the power supply voltage is less than 20 Volts
DC. Use only the correct size ( ½ amp) and type (fast blow)
fuse – or severe damage to the unit will likely occur.
Check the RPM pickup on the dynamometer. Be sure that it
is not loose. Check the wiring from the RPM pickup to the
horsepower computer. Make sure the RPM sensor connector
is tight. Have the horsepower computer checked.
Check the load cell on the dynamometer. Be sure that it is
not loose. Check the cable between the load cell and the
horsepower computer. Make sure the Torque Sensor
connector is tight. The load cell may be bad and need to be
replaced. Have the horsepower computer checked.
Check the printer cable between the horsepower computer
and the printer. Be sure both ends are tight in their
respective connectors. Make sure the printer is plugged into
a proper power source. Perform a “self test” on the printer to
be sure it is working. Have the horsepower computer
checked.
Check the torque calibration. If Chassis dyno, the tires may
be slipping on the dynamometer rolls – increase chain
tension to obtain more “over center” action between tires
and rolls. Excess speed often causes power losses. If farm
tractor, the PTO clutch may be slipping (refer to the tractor
repair manual). Engine may not be performing properly.
Have the horsepower computer checked.
Operate the unit in the CHECK function. If the reading is
not 4000 RPM, have the horsepower computer repaired. If
the CHECK reading is 4000 RPM, check the RPM pickup

16

Torque readings are
inaccurate

Residual Torque readings
are high when the
dynamometer is stopped.

and the RPM sensor gear. Make sure that they are not loose
and that the runout of the RPM gear is not excessive. Check
the RPM sensor connector to be sure that it is tight. Check
the cable from the RPM pickup to the horsepower computer.
Check the power supply to the horsepower computer. Have
the horsepower computer checked.
Operate the unit using the ZERO and CHECK functions. If
the readings do not agree with the tables above, unit needs
to be repaired. Check the load cell mounting to be sure that
it is not loose. Check the dynamometer to be sure that it is
not in a bind. Check the torque calibration of the
horsepower computer. Check the power supply to the
horsepower computer. Have the horsepower computer
checked.
Pressure or force on the dynamometer absorption unit cradle
may be causing the residual readings. Remove the load cell
from the torque arm of the dyno to see if this removes the
excessive residual torque reading. Manually rock the torque
arm of the dyno. It should move freely and easily a
minimum of 0.5 inches (12.7 mm) up and down. The load
cell must be in a free floating position when not under load.
Re-adjust the torque cable and connectors if necessary.
Check the calibration zero of the horsepower computer.
The load cell may be damaged and need to be replaced.
Have the horsepower computer checked.

17