Model ACC-52 - Hoffer Flow Control

Model ACC-52
DC Powered Version
Mag Coil Flow Rate Conditioner Frequency to Flow Alarm
USER’S MANUAL
HP-252
September 2004
107 Kitty Hawk Lane ● P.O. Box 2145 ● Elizabeth City, NC 27909
1-800-628-4584 ● (252) 331-1997 ● Fax (252) 331-2886
www.hofferflow.com
email: info@hofferflow.com
Notice
HOFFER FLOW CONTROLS, INC. MAKES NO WARRANTY OF ANY KIND
WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE.
This manual has been provided as an aid in installing, connecting, calibrating, operating, and
servicing this unit. Every precaution for accuracy has been taken in the preparation of this
manual; however, HOFFER FLOW CONTROLS, INC. neither assumes responsibility for any
omissions or errors that may appear nor assumes liability for any damages that may result from
the use of the products in accordance with information contained in the manual.
HOFFER FLOW CONTROLS' policy is to provide a user manual for each item supplied.
Therefore, all applicable user manuals should be examined before attempting to install or otherwise
connect a number of related subsystems.
During installation, care must be taken to select the correct interconnecting wiring drawing. The
choice of an incorrect connection drawing may result in damage to the system and/or one of the
components.
Please review the complete model number of each item to be connected and locate the appropriate
manual(s) and/or drawing(s). Identify all model numbers exactly before making any connections.
A number of options and accessories may be added to the main instrument, which are not shown
on the basic user wiring. Consult the appropriate option or accessory user manual before
connecting it to the system. In many cases, a system wiring drawing is available and may be
requested from HOFFER FLOW CONTROLS.
This document contains proprietary information, which is protected by copyright. All rights are
reserved. No part of this document may be photocopied, reproduced, or translated to another
language without the prior written consent of HOFFER FLOW CONTROLS, INC.
HOFFER FLOW CONTROLS’ policy is to make running changes, not model changes,
whenever an improvement is possible. This affords our customers the latest in technology and
engineering. The information contained in this document is subject to change without notice.
RETURN REQUESTS / INQUIRIES
Direct all warranty and repair requests/inquiries to the Hoffer Flow Controls Customer Service Department, telephone
number (252) 331-1997 or 1-800-628-4584. BEFORE RETURNING ANY PRODUCT(S) TO HOFFER FLOW
CONTROLS, PURCHASER MUST OBTAIN A RETURNED MATERIAL AUTHORIZATION (RMA) NUMBER FROM
HOFFER FLOW CONTROLS’ CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID PROCESSING
DELAYS). The assigned RMA number should then be marked on the outside of the return package and on any
correspondence.
FOR WARRANTY RETURNS, please have the
following information available BEFORE contacting
HOFFER FLOW CONTROLS:
1. P.O. number under which the product was
PURCHASED,
2. Model and serial number of the product under
warranty, and
3. Repair instructions and/or specific problems relative
to the product.
HFC 9708
FOR
REPAIRS
OR
NON-WARRANTY
consult
HOFFER
FLOW
CALIBRATIONS,
CONTROLS for current repair/calibration charges. Have
the following information available BEFORE contacting
HOFFER FLOW CONTROLS:
1. P.O. number to cover the COST of the
repair/calibration,
2. Model and serial number of the product, and
3. Repair instructions and/or specific problems relative
to the product.
LIMITED WARRANTY
HOFFER FLOW CONTROLS, INC. ("HFC") warrants HFC's products ("goods") described in the specifications
incorporated in this manual to be free from defects in material and workmanship under normal use and service, but only if
such goods have been properly selected for the service intended, properly installed and properly operated and maintained.
This warranty shall extend for a period of one (1) year from the date of delivery to the original purchaser (or eighteen (18)
months if the delivery to the original purchaser occurred outside the continental United States). This warranty is extended
only to the original purchaser ("Purchaser"). Purchaser's sole and exclusive remedy is the repair and/or replacement of
nonconforming goods as provided in the following paragraphs.
In the event Purchaser believes the goods are defective, the goods must be returned to HFC, transportation prepaid by
Purchaser, within twelve (12) months after delivery of goods (or eighteen (18) months for goods delivered outside he
continental United States) for inspection by HFC. If HFC's inspection determines that the workmanship or materials are
defective, the goods will be either repaired or replaced, at HFC's sole determination, free of additional charge, and the goods
will be returned, transportation paid by HFC, using he lowest cost transportation available.
Prior to returning the goods to HFC, Purchaser must obtain a Returned Material Authorization (RMA) Number from HFC's
Customer Service Department within 30 days after discovery of a purported breach of warranty, but no later than the
warranty period; otherwise, such claims shall be deemed waived. See the Return Requests/Inquiries Section of this manual.
If HFC's inspection reveals the goods are free of defects in material and workmanship or such inspection reveals the goods
were improperly used, improperly installed, and/or improperly selected for service intended, HFC will notify the purchaser
in writing and will deliver the goods back to Purchaser upon (i) receipt of Purchaser's written instructions and (ii) the cost of
transportation. If Purchaser does not respond within thirty (30) days after notice from HFC, the goods will be disposed of in
HFC's discretion.
HFC does not warrant these goods to meet the requirements of any safety code of any state, municipality, or other
jurisdiction, and Purchaser assumes all risk and liability whatsoever resulting from the use thereof, whether used singly or in
combination with other machines or apparatus.
This warranty shall not apply to any HFC goods or parts thereof, which have been repaired outside HFC's factory or altered
in any way, or have been subject to misuse, negligence, or accident, or have not been operated in accordance with HFC's
printed instructions or have been operated under conditions more severe than, or otherwise exceeding, those set forth in the
specifications for such goods.
THIS WARRANTY IS EXPRESSLY IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED,
INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE. HFC SHALL NOT BE LIABLE FOR ANY LOSS OR DAMAGE RESULTING, DIRECTLY OR INDIRECTLY, FROM THE USE OR
LOSS OF USE OF THE GOODS. WITHOUT LIMITING THE GENERALITY OF THE FOREGOING, THIS EXCLUSION FROM LIABILITY
EMBRACES THE PURCHASER'S EXPENSES FOR DOWNTIME OR FOR MAKING UP DOWNTIME, DAMAGES FOR WHICH THE PURCHASER
MAY BE LIABLE TO OTHER PERSONS, DAMAGES TO PROPERTY, AND INJURY TO OR DEATH OF ANY PERSONS. HFC NEITHER
ASSUMES NOR AUTHORIZES ANY PERSON TO ASSUME FOR IT ANY OTHER LIABILITY IN CONNECTION WITH THE SALE OR USE OF
HFC'S GOODS, AND THERE ARE NO ORAL AGREEMENTS OR WARRANTIES COLLATERAL TO OR AFFECTING THE AGREEMENT.
PURCHASER'S SOLE AND EXCLUSIVE REMEDY IS THE REPAIR AND/OR REPLACEMENT OF NONCONFORMING GOODS AS PROVIDED IN THE
PRECEDING PARAGRAPHS. HFC SHALL NOT BE LIABLE FOR ANY OTHER DAMAGES WHATSOEVER INCLUDING INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES.
HFC 9708
TABLE OF CONTENTS
SECTION I
INTRODUCTION AND SPECIFICATIONS................................................................1.1
SECTION II
INSTALLATION ...........................................................................................................2.1
SECTION III
CALIBRATION .............................................................................................................3.1
SECTION IV
OPERATION .................................................................................................................4.1
SECTION V
MAINTENANCE AND MAIN SCHEMATIC ..............................................................5.1
ACC- 52
HP - 252
ACC-52
HP-252
SECTION I
GENERAL
The Model ACC-52 is a flowrate converter which provides a flowrate alarm output with a user
programmable alarm trip point and also provides a voltage output proportional to flowrate. A
conditioned pulse output with limited pulse scaling is also provided for applications involving remote
transmission of a frequency or pulse output.
Two basic versions of the ACC-52 are available depending on the number of alarm trip points required.
The standard version offers a single trip point with a ten turn alarm trip point dial. The second version
has two alarm trip points with a 270° scale and with a more limited selection of alarm output types.
Alarm Outputs are available in the forms of Open Collector, TTL/CMOS, and Low Power Relay
types.
The analog output voltage signal is directly proportional to input frequency generated by the flowmeter
as a linear function of flowrate. Several Ranges are available. Span and Zero Controls are provided.
Several Output Pulse configurations are available which offer flexibility in choosing the interface required
by the host system. The output is available in TTL/CMOS and Open Collector configurations. Switch
selectable binary pulse scaling of divide by 1, 2, 4, 8, 16 and 32 are standard with divide by 64 and
128 optionally available on special order. The pulse scaling is intended to reduce the output pulse
frequency where required.
The input signal conditioning circuitry is designed for use with flowmeters equipped with magnetic
pickups. The input circuitry accepts the low level turbine flowmeter signal while providing rejection of
unwanted noise and spurious signals. A signal threshold control allows the user to set the input
sensitivity above the background noise level, thereby eliminating any false signal from being accepted.
As a member of the Hoffer ACC Series of Turbine Flowmeter Interface Accessories, the ACC-52 is
enclosed in the standard Style 2 enclosure thereby providing a compact assembly suitable for mounting
indoors. Optional enclosures provide for Nema-4 and Explosion Proof service ratings.
The ACC-52 is available with power options of 15-35 VDC and 115 VAC 50/60 Hz.
ACC-52
1.1
HP-252
SPECIFICATIONS
SIGNAL INPUT
General
Magnetic Pickup Compatible. Input Protected, RF and
Bandpass Filtered. Adjustable Trigger Level.
Input Impedance
40 K-Ohm (Nominal).
Trigger Sensitivity
10 mVrms.
Input Frequency Range
10 to 2500 Hz
Over-voltage Protection Limit
130 Vrms
ALARM TRIP POINTS
Single Alarm
10 turn dial calibrated 0 - 100% of span.
Dual Alarm
Two 0 to 270° rotation calibrated 0 - 100% of span.
Deadband
2% of span.
Setpoint Accuracy
1% span.
ALARM OUTPUTS
Table A - Alarm Output Matrix
Output Type
TTL/CMOS
Open Collector
Relay
Above Alarm
Logic 1
OFF
OFF
Below Alarm
Logic 0
ON
Energized
Power Fail
5.6 Kohms
OFF
OFF
Response Time
Two second delay on alarm for 0 to 110% of trip point
input excitation.
TTL/CMOS
Logic 1 (TTL) 2.4 VDC at -0.5 mA
Logic 1 (CMOS) 4.5 VDC at -0.1 mA
Logic 0 -- 0.4 VDC at 100 mA
Open Collector
Maximum OFF State Voltage -- 60 VDC.
Saturation Voltage -- 0.4 VDC (100 mA).
Relay Output
Form C.
Contact Rating
0.6 @ 125 VAC, 0.6 @ 110 VDC and 2 @ 30 VDC
ACC-52
1.2
HP-252
SPECIFICATIONS (CONTINUED)
ANALOG OUTPUT
Available Range Options
0 to 5 VDC and 0 to 10 VDC
Output Impedance
5 ohms
Minimum Load Resistance
1000 ohms
Linearity
0.1% FS (0.05% FS Typical)
Temperature Effects
250 PPM/degree C
Response Time (10 - 90%)
0.5 seconds
Short Circuit Protection
Current limited for shorts to common at about 15 mA.
Effect of Line Power Variations
0.0025% Span/% Line Variation
PULSE OUTPUT
Available Forms
TTL/CMOS, Open Collector, HTL
Pulse Scaling
Divide by 1, 2, 4, 8, 16, 32 standard.
Divide by 64, 128 special order.
Open Collector
Maximum Collector OFF Voltage =
Maximum ON Current 1 amp.
TTL/CMOS
4.5 VDC at 1.2 mA.
0.4 VDC at 100 mA.
60 V.
POWER
AC Option
115 ±10%
DC Option
15 to 35 VDC.
ENVIRONMENTAL
Enclosure
ACC Series Style-2 Standard.
Explosion Proof and NEMA-4 Optional
Operating Temperature
-40 to 85 degrees Centigrade.
Warm-up Time
10 minutes
ACC-52
1.3
HP-252
CONTROLS AND ADJUSTMENTS
ALARM TRIP SETPOINT
Single Alarm Option
A ten turn control with a dial calibrated 0 to 100% of span.
Dual Alarm Option
270 degree rotation over scale with 25 graduations from 0 to 100%.
Course Range
Six position DIP switch located on the PCA-95. Used to select the
range of the input frequency.
Fuse
A circuit protection device on the PCA-94 for AC power option.
Scaling Factor
A six position DIP Switch located on the PCA-95. Used to select pulse
output scaling factor.
Sensitivity
A 20 turn, external adjustment used to set the input trigger threshold above
the background noise pickup.
Span
A 20 turn, external adjustment to set the span of the analog output.
Zero
A 20 turn, internal adjustment to set the zero of the analog output.
ACC-52
1.4
HP-252
SECTION II
FLOWMETER INSTALLATION
GENERAL
Proper application of the turbine flowmeter requires a suitable piping installation in order to achieve
accurate and reliable operation.
The piping configuration immediately preceding and following the flowmeter is termed the meter run. Refer
to the manufacturer's outline and installation instructions when installing the flowmeter and meter run.
RELATIVE - The performance of the turbine flowmeter is affected by the fluid swirl and non-uniform
velocity profiles. The following recommendation will reduce such flow irregularities.
It is advisable not to locate the meter run immediately downstream of pumps, partially opened valves,
bends or other similar piping configurations. In addition, the area surrounding the flowmeter should be free
of sources of electrical noise such as motors, solenoids, transformers and power lines which may be
coupled to the pickoff device.
The metering section should not be subjected to excessive vibration or shock. Such a condition may result
in an mechanically induced output signal from the pickoff device.
METER RUN - In general, the meter run should be chosen to have the same inner diameter as the meter
bore. A minimum of 10 pipe diameters of straight pipe upstream and 5 pipe diameters downstream are
required. Where this optimum line configuration can not be implemented, it is advisable to install a flow
straightener properly positioned upstream of the flowmeter. Orientation is not a critical factor, however,
horizontal is a preferred orientation.
BYPASS - A properly sized bypass run with suitable blocking valves may be equipped where an
interruption in fluid flow for turbine meters servicing can not be tolerated.
STRAINER - A strainer, filter and/or air eliminator is recommended to reduce the potential of fouling or
damage. See table for recommended mesh size.
On initial startup of a line, it is advisable to install a spool piece purging the line to eliminate damaging the
flowmeter, due to flux, tape, solder, welds or other contaminates carried along by the fluid stream.
CAVITATION - Cavitation causes measurement inaccuracies in turbine flowmeter and should be avoided
by suitable line and operating configurations.
Whenever the pressure within a pipeline instantaneously falls below the equilibrium vapor pressure of the
fluid, a portion of the fluid vaporizes and forms bubbles in the pipeline. This is termed cavitation. Cavitation
is eliminated by maintaining adequate back pressure on the flowmeter. A downstream valve that provides
the necessary back pressure is one means for preventing cavitation in the metering run. Control valves
should be located downstream, if possible. Some installations may also make use of a vapor eliminator
upstream of the flowmeter.
ACC-52
2.1
HP-252
The minimum required back pressure may be estimated using Equation A:
Equation A - Back Pressure Equation
Min: Back Pressure = 1.25 X Vapor Pressure + 2 X Pressure Drop
INSTALLATION WIRING LAYOUT FOR INTERCONNECTIONS
In considering the interconnection between the flowmeter and the flow measurement system some attention
must be given to anticipated noise sources and to the coupling of these noise sources to the interconnecting
wiring.
Noise signals may be coupled inductively or capacitvely into the wiring between the flowmeter and the
electronic measuring systems. In general, utilizing a shielded, twisted pair for the interconnection greatly
reduces this coupling. The shield should be grounded on one end of the cable only. In general, grounding
only on the electronic measuring system is best.
However, even with proper interconnecting cabling crosstalk with other signal lines or power lines may still
occur and should be avoided. Physical isolation in the manner in which the wiring is run reduces the
chances of potential problems.
It is common to transmit the low level output signal from the flowmeter several hundred feet through a
shielded, twisted pair instrument cable. Where a noise environment is suspect, it is recommended that a
preamplifier be installed on or near the flowmeter to assure the preservation of flow information from the
flowmeter to the electronic measuring system. Suitable accessory models are available from manufacturer.
PLANNING THE INSTALLATION OF THE ACC-52 (DC VERSION)
The ACC-52 should be placed in a convenient location which maintains access to the unit should repairs or
readjustment be required.
Refer to the case outline and installation drawing for the appropriate case type to be installed. Drill
appropriate mounting holes as required.
Refer to the wiring installation drawing for appropriate terminals for the interconnections. Connections to
the terminal block should be carefully dressed to avoid having bare wires extending pass the screw clamp
on the terminal block. This is particularly important for units mounted in an explosion proof enclosure.
Wiring should be neatly dressed near the bottom of the enclosure to assure the wiring will not become
fouled when the cover is installed.
Connect the two conductor shielded cable from the flowmeter. Connect the shield to the ACC-52 only.
Connect the analog voltage output to the desired, compatible receiving instrument if used. Be sure to
observe polarity at the receiving end. Shielded wiring is recommended.
Connect the pulse output to the desired, compatible receiving instrument. Be sure to observe polarity.
Shielded wiring is recommended.
Connect the alarm output to the desired alarm receiving device, be certain that the alarm output type
desired is the same as that supplied.
The power source voltage should be the same as that specified in the model number and of the correct
type AC/DC. Connection to the power should be made through a circuit breaker so that power can be
turned off while servicing the unit. An earth ground is required in most instances to properly terminate
shields.
ACC-52
2.2
HP-252
THIS PAGE LEFT INTENTIONALLY BLANK.
ACC-52
2.3
HP-252
SECTION III
CALIBRATION OF ANALOG OUTPUT - GENERAL CONSIDERATIONS
INTRODUCTION
In general, all flow measurement systems supplied by Hoffer Flow Controls have been factory calibrated as
specified by the user, at the time of purchase, free of charge.
All systems which underwent such a factory calibration have a calibration card attached prior to shipment.
This card contains the details of analog outputs, as well as other useful calibration data.
Field calibration is only required when a change has occurred or is sought to the measuring system. Such a
change may be due to repair, replacement or recalibration of the flowmeter, or perhaps a change in the
analog output span.
PROCEDURE
Begin by determining the equivalent maximum volumetric flowrate in GPM, expected by the application,
term this GPM (MAX). GPM (MAX) may be calculated based on the analog output scale requirements or
may be the maximum flowrate listed on the flowmeter’s calibration sheet.
From the calibration constant (or K Factor) listed on the data sheet for the flowmeter, obtain the frequency
corresponding to GPM (MAX) using Equation B and designate this frequency F (MAX).
Equation B - Frequency Equation
F MAX = K AVG X GPM MAX
60
FOR ANALOG OPTION
The analog output of the ACC-52 may be calibrated with the aid of an external oscillator used in
conjunction with a frequency counter.
The external oscillator is used to supply a test frequency. In this method, the external oscillator is connected
to the signal input terminals as shown in Figure 1. The oscillator’s output frequency is set to equal F
(MAX) as indicated on the frequency counter.
1.
The course range adjustment is accomplished by selecting a switch position on a DIP switch located
on the PCA-57 printed circuit card. See Table A to determine required switch position and set into
switch as shown on drawing ACC-52-403 for anticipated F Max.
ACC-52
3.1
HP-252
2. Connect a digital voltmeter or equivalent, across the voltage output terminals.
3. Adjust ZERO control for desired zero voltage (i.e., .001 VDC, .000 VDC).
4. Turn SPAN POT fully CCW until detent is felt or 25 turns.
5. Inject the Test Frequency equal to F (MAX) while adjusting SPAN for voltage equal to +5.000 V ±1
mV. See test setup shown in Figure 1.
NOTE:
Iterate steps 3 and 4 until no change is observed.
FOR PULSE SCALING OPTION
1.
An optional DIP switch is located on the PCA-95 printed circuit card. See Table C to determine
required switch position and set into switch, as shown in the Controls and Adjustments drawing,
for required divide by N.
2.
For a required divide by 64 or 128 switch position 6 must be jumpered as shown in the Controls
and Adjustments drawing (ACC-52-401).
Table B - Analog Switch Position
F (MAX)
75 TO 150
150 TO 300
300 TO 600
600 TO 1200
1200 TO 2400
2400 TO 4300
*NOTE:
Table C - Pulse Scaling Switch Position
RANGE SELECT
SWITCH POSITION
1
2
3
4
5
6
)N
SWITCH POSITION
1
2
4
8
16
32
64*
128*
1
2
3
4
5
6
For divide by 32, 64, or 128, switch position 6 is jumpered to appropriate location
on PCA-52 printed circuit board.
CALIBRATION AND SETUP OF THE ACC-52 ALARMS
The alarm trip points are selected by an adjustment which has a calibrated scale of 0-100% of the span of
the analog output.
In the ACC-52, the span of the analog output is established during the preceding calibration procedure.
ACC-52
3.1
HP-252
To calculate the alarm trip point setting in percent of the full scale span, perform the following calculation:
Equation C - Determining Alarm Trip Point Setting
Given:
Full Scale Flowrate of analog output in GPM
Desired Flowrate Trip Point in GPM
Alarm Setting in Percent =
Trip Point GPM
Full Scale GPM
X 100%
In some configuration of the ACC-52, more than one alarm trip point is supplied. In this case the above
equation is recalculated for the second alarm trip point.
The calibration dials for the alarm trip point make selecting the trip point easy.
There are several forms of the alarm outputs available. Single alarms are available in Form C relay output,
TTL/CMOS logic level and finally in the form of a "NPN" type open collector transistor. Dual alarm types
only offer TTL/CMOS and open collector configurations. The alarm output form is a factory equipped
option.
ACC-52
3.3
HP-252
SECTION IV
INITIAL STARTUP OF THE ACC-52
PURGING OF DEBREE FROM THE LINE
Perform any purging of the piping with a spool piece installed in place of the flowmeter. Once completed,
install the flowmeter and connect the cabling to the flowmeter pickup coil.
SENSITIVITY ADJUSTMENT PROCEDURE
Noise pickup may cause undesirable outputs from the ACC-52 during periods of little or no flow. If false
outputs occur turn the sensitivity control counterclockwise till false output stops.
INITIAL OPERATIONAL CHECKOUT
Verify that the alarms, analog output and pulse outputs are functioning properly.
GENERAL OPERATION OF THE ACC-52
The pulse output, analog output, and alarm(s) function automatically when flow commences.
The ACC-52 will generate the desired voltage output proportional to flowrate as specified in the model
numbering system. That is either 0-5 VDC or 0-10 VDC. The span will correspond to that established
during the calibration section. The load resistance should be greater than the minimum specified.
The pulse output will be of the form specified in the model numbering system and will be a square wave
whose frequency is equal to the input frequency divided by the scaling factor selected during the setup of
the instrument.
The alarm outputs will be the type specified in the model numbering system and will activate at the flowrate
for which they are set.
Any questions which arise regarding incompatibility with receiving instruments may be addressed to the
engineering group at Hoffer Flow Controls, Inc.
ACC-52
4.1
HP-252
THEORY OF OPERATION
The Block Diagram of the ACC-52 drawing has key features, as well as, information flow designated.
Refer to this drawing for the following discussion.
The frequency signal proportional to flowrate enters the ACC-52 from the flowmeter through the "SENS"
control which is used to attenuate unwanted noise. The amplifier and comparitor from a signal conditioning
section. The input signal conditioning circuitry is designed for use with magnetic pickups which generate a
compatible signal over the frequency range usually generated by turbine flowmeters.
The signal is then passed to a pulse scaling network to an output transistor buffer. The pulse scaling
network is used to reduce the frequency from the flowmeter to slow enough rate to be compatible with the
receiving data acquisition system. The pulse output buffer transistor allows a convenient means of offering a
number of different pulse output configurations and drive levels.
The frequency signal from the flowmeter is also passed to a precision frequency to voltage converter. This
circuit has zero and span adjustments. The output from the F/V Converter is sent to the analog output
amplifier and to the alarm comparitors.
The analog output amplifier functions as a buffer amplifier providing the required drive current for the
output and isolating the output from the alarm function. A short on the analog output does not effect the
alarm.
The alarm comparitors compare the voltage proportional to the current flowrate to the setpoint voltage
proportional to the alarm trip point. The state of the alarms is set or cleared appropriately.
Several forms of the alarm output may be provided based on the components supplied on the alarm
comparitor output. These are factory wired options. There are limitations on the form of the output alarms
when more than one alarm trip point is supplied.
The power supply circuitry for the AC power option consists of a fuse, a transformer, power rectifiers,
power input filter, and regulators which provide the required internal bias voltages of +5 and +12 VDC. A
DC/DC converter is used to generate a -5 VDC supply which allows for true zero in the analog output. A
precision +2.5 volt reference is also generated for use by the alarm setpoints. The shield ground is
terminated to the earth ground of the line power input.
The power supply circuitry for the DC power option has no fuse or transformer. The rectifiers are used to
provide reverse polarity protection. The shield ground is terminated by the third power wire labeled chassis
ground.
ACC-52
4.2
HP-252
THIS PAGE LEFT INTENTIONALLY BLANK.
ACC-52
4.3
HP-252
SECTION V
MAINTENANCE, GENERAL
Hoffer Flow Controls Flow Measurement Systems are constructed to give a long service life in the targeted
measuring field and service environment. However, problems do occur from time to time and the following
points should be considered for preventative maintainence and repairs.
The bearing type used in the flowmeter was chosen to give compromise between long life, chemical
resistance, ease of maintenance and performance. A preventative maintenance schedule should established
to determine the amount of wear which has occurred since last overhaul. See user's manual for flowmeter
for further instructions.
A spare parts list has been provided which, at the discretion of the user, may be user stocked. Consult with
the manufacturer is an abridged spare parts list is sought. The recommended spare parts list may be found
following this section and in the user's manual for the flowmeter.
In case the flow measurement system malfunctions or becomes inoperative, a troubleshooting procedure is
enclosed.
Factory consultation is available to assist in diagnosing problems. In addition, factory repair parts and
service are available for individuals who wish to utilize this service.
A complete set of schematic diagrams for all printed cards is available from Hoffer Flow Controls, Inc. for
users who wish their own personnel to service the measuring system.
NOTE:
All printed circuit cards are warranteed for one year after date of sale.
All printed circuit cards may be factory repaired at a nominal fee for parts and labor
after warrantee period.
Table B - Recommended Spare Parts List
Model ACC-52 Frequency/Voltage Flow Alarm Subsystem
Part Number
Description
Quantity
1/20 Amp
Fuse, Power Supply
1 Box
ACC52-XX
Conditioner/Converter
1
PC-XX-XX
Coil
1
NOTE:
ACC-52
Additional spare parts may be recommended for the turbine flowmeter. See user's
manual for turbine flowmeter for details.
5.1
HP-252

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