Obvius A90DC-12 User manual

A90DC-12 – DC Current Monitor
Obvius, LLC
Installation and Operation Manual
Model A90DC-12, A90DC-10
Date: Sep , 2013
Page 1 A90DC-12 – DC Current Monitor
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Copyright Information
Copyright © 2007 - 2013 by Obvius
Obvius, AcquiSuite and ModHopper are trade arks of Obvius Holdings LLC
Other brand and product na es are trade arks or registered trade arks of their respective holders.
U.S. Government Restricted Rights: Use, duplication or disclosure by the Govern ent is subject to restrictions set fourth in subparagraph (a) through
(d) of the Co ercial Co puter Restricted Rights clause at FAR 52.227-19 when applicable, or subparagraph (c) (1) (ii) of the Rights in Technical Data
and Co puter Software clause at DFARS 252.227-7013, and in si ilar clauses in the NASA FAR Supple ent.
Limited Warranty
OBVIUS IS PROVIDING THIS WARRANTY IN LIEU OF ALL OTHER EXPRESS OR IMPLIED WARRANTIES, INCLUDING ANY WARRANTY
OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. THIS WARRANTY IS BUYER'S EXCLUSIVE REMEDY FOR ALL
CLAIMS AGAINST OBVIUS. OBVIUS SHALL NOT BE LIABLE FOR ANY CONSEQUENTIAL OR INCIDENTAL DAMAGES. OBVIUS'S TOTAL
LIABILITY FOR ALL CLAIMS SHALL BE LIMITED TO THE PRICE PAID FOR ITS PRODUCT.
Obvius pro ises buyer that any standard product anufactured by Obvius shall be free fro all aterial defects in design, aterial, or anufacturing for
a period of 2 years fro the anufacture date; provided, however, that the warranty shall not extend to ordinary wear and tear or to nor ally replaceable
co ponents (e.g., batteries). During the warranty period, Obvius ay repair or replace (in its sole discretion) any product suffering fro a warranty defect
and returned freight prepaid by buyer, with no charge to buyer for any warranty repair or replace ent. The warranty shall re ain in full force and effect
for such 2 year period, provided that the product: (1) was installed, operated, and aintained properly; (2) has not been abused or isused; (3) has not
been repaired, altered, or odified outside of Obvius's authorized facilities; (4) has not been sold subject to other warranty ter s specified at the ti e of
sale; and (5) is still owned by the original purchaser. This warranty provides specific legal rights that ay be varied by state law. Obvius's products are not
designed for life or safety applications.
Product Application Limitation
Obvius strongly believes in continuous i prove ent, therefore we ust reserve the right to change specifications and product offerings without notice.
Where possible, we will substitute products with equivalent functionality when necessary.
DANGER
Hazard of Electric Shock, Explosion or Arc Flash
●Follow safe electrical work practices. See NFPA 70E in the USA, or applicable local codes.
●This equipment must only be installed and serviced by qualified electrical personnel.
●Read, understand and follow the instructions before installing this product.
●Turn off all power supplying equipment before working on or inside the equipment. Use properly rated voltage sensing device to
confirm power is off. DO NOT DEPEND ON THIS PRODUCT FOR VOLTAGE INDICATION
●Only install this product on insulated conductors.
Failure to follow these instructions will result in death or serious injury.
NOTICE
●This product is not intended for life safety applications.
●Do not install this product in hazardous or classified locations.
●The installer is responsible for conformance to all applicable codes.
●Mount this product inside a suitable fire and electrical enclosure.
FCC Part 15 Information
Note: This equipment has been tested by the manufacturer and found to comply with the limits of a class A digital device, pursuant to part
15 of the FCC rules. These limits are designed to provide reasonable protection against interference when the equipment is operated in a
commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in
accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a
residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own expense.
Modifications of this product without the express authorization of Obvius nullify this statement.
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Table of Contents
Markings and Sy bols:...............................................................................................................................................................3
Overview......................................................................................................................................................................................4
Applications.................................................................................................................................................................................4
Installation Checklist...................................................................................................................................................................4
Hardware Overview.....................................................................................................................................................................5
A90DC-12, A90DC-10 Series Features and Specifications...................................................................................................5
Power and Co unication Connections...............................................................................................................................6
Hardware Installation.............................................................................................................................................................6
Te perature...........................................................................................................................................................................8
Monitoring usage:........................................................................................................................................................................9
AcquiSuite Advanced Configuration Options................................................................................................................10
Modbus Features........................................................................................................................................................................11
Supported Modbus Functions..............................................................................................................................................11
Modbus Register List...........................................................................................................................................................11
Register for atting.........................................................................................................................................................14
Alar configuration.......................................................................................................................................................14
Mechanical Drawings................................................................................................................................................................15
A90DC-12 Fir ware Update.....................................................................................................................................................16
Markings and Symbols:
WARNING: A potential risk exists if the operating instructions are not followed
General Warning Sy bol: This sy bol indicates the need to consult the operating instructions provided with the
product.
This sy bol indicates the presence of electric shock hazards.
This sy bol indicates: Do not apply to or re ove fro hazardous live conductors.
Direct Current sy bol.
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Overview
The A90DC-12 DC Series current onitor syste is designed to allow easure ent and alar ing of DC current
applications including solar pv arrays, battery onitoring and DC power supplies for teleco switch gear.
The A90DC-12 uses 12 non-contact DC Hall Effect sensors to easure DC current on each of the 12 channels. DC current
can be easured in both directions, showing positive and negative nu bers in the resulting easure ent values. Data
values are ade available via RS485 serial using the standard Modbus RTU protocol.
In addition to reporting the current values of each channel, the A90DC-12 also provides alar functions to onitor
i balances between channels. This feature is instru ental in detecting failed equip ent in applications such as Solar PV
arrays.
Applications
The A90DC-12 Series DC Current Monitor has several applications. These include:
●DC Load Monitoring.
●Solar PV Power Generation
●Battery Charge and Discharge onitoring.
Installation Checklist
An A90DC-12 syste installation has the following co ponents:
Required hardware
●A90DC-12 Series DC current onitor (required)
●24VDC power supply
●Data connection to a Modbus aster device such as an AcquiSuite, ModHopper, PLC or co puter software such as
the Obvius Config Console.
●Enclosure for the A90DC-12 DC to satisfy UL safety require ents.
●Shielded twisted pair wire for co unications.
Note: If using the Obvius Config Console software, an RS232/DB9 or RS485 serial cable will be required to attach the
A90DC-12 to the co puter.
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Hardware Overview
A90DC-12, A90DC-10 Series Features and Specifications
Processor Ar 7 e bedded CPU
LED Alive (green), RS485 TX, RX (yellow)
Protocol Modbus RTU
Addressing Modbus address ay be set fro 1 to 247 via Modbus register.
Power Supply Power input : 9-30vdc at 1.25W. (power supply not included)
140 A typical at 9vdc, 55 A typical at 24vdc. (excluding the 4-20 A sensor input channel)
Note: 24vdc required for use of the 4-20 A analog input port. When fully loaded, the axi u
current should not exceed 250 A.
Transient overvoltage rating 1500V
Current Inputs212 DC Hall Effect Sensors, non-contact.
Maxi u range +15A ps to -15A ps DC
The product is intended to easure insulated and uninsulated conductors and to be installed inside a
Listed electrical and fire enclosure.
0.49 inch by 0.35 inch opening for load wire.
Accuracy: +/- 5% of full scale (+/- 0.75A) at 25ºc
Analog input1: 4-20 A analog input:
Measure ents DC current per channel, instantaneous and average
Total DC current (su of 12 channels), instantaneous and average
Average DC current (of 12 channels), instantaneous and average
Alar ing Low alar ay set as a percent of DC average of other channels.
Alar s ay be disabled below a ini u average current level.
Mini u ti e for alar ay be set to prevent alar s on brief events.
Unused channels ay be disabled to exclude the fro total and average calculations.
Co unications1RS-485 (+,-, S), 9600 baud, N, 8, 1, two wire. Supports up to 32 external devices (expandable)
Isolation The RS485 ter inals electrically isolated to 1500V fro the re ainder of the A90DC-12 board.
Environ ental2North A erica: Te perature -30º – 70ºc, 0 – 95% hu idity, non-condensing.
Altitude up to 2000M.
For indoor and outdoor use when used in an appropriate enclosure.
The A90DC-12 ust be ounted inside a NEMA rated electrical enclosure for safety and isolation
require ents.
Safety UL61010 Recognized
File: E320540 (Model3 A90DC-12, A90DC-10)
EMC FCC CFR 47 Part 15, Class A
Size 12.85” x 2.5” x 1.75” (326 x 64 x 45 )
Mass 0.83 lbs (0.375 kg)
Measure ent Category IV applications2 (Cat IV):
up to 600vdc Pollution Degree 2: no insulation required
up to 1000vdc Pollution Degree 3: with basic insulation (wire insulation ust be rated to 1000v)
1 Outputs are intended for low voltage class 2 inputs.
2 If the product is used in a anner not specified by the anufacture, the protection provided by the equip ent ay be
i paired.
3 Note: The A90DC-12 or A90DC-10 odels are identical except for the nu ber of DC current sensor channels present on
the device. This anual will refer to odel A90DC-12 however the anual covers installation and operation for all three
odels except where otherwise noted.
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Power and Communication Connections
Hardware Installation
Step 1 - Unpack aterials: Re ove all aterials fro shipping box and verify all required co ponents are available
Step 2 - Mount the A90DC-12 inside the electrical enclosure. Be sure to provide enough roo to route the load wires
through the hall effect sensor openings.
Step – Attach the power supply to the A90DC-12. Be sure to observe the polarity. Note: Power can be
disconnected by re oving the screw ter inal plug fro the A90DC-12 power connection socket.
The A90DC-12 can operate on
Step 4 - Connect the RS485 Modbus network loop as shown in the wiring diagra . Follow the anufacturer’s instructions
for installing and powering the Modbus Master device. Verify that the Modbus address settings are unique for each device
(i.e., no two devices with the sa e address). Connect each device in the chain by “daisy-chaining” the devices together .
Observe + and - polarity on the Modbus devices. For ore infor ation about Modbus loops, please read our Modbus FAQ
available at .
Do not ground the RS485 shield inside the electrical panel. All RS485 and 24vdc power wires, including the shield should
be insulated to prevent accidental contact to high voltage conductors.
The RS485 and 24vdc power cable should be echanically secured where it enters the electrical panel.
The wire used to provide RS485 co unications should be insulated to eet require ents of the voltages present inside the
box that the A90DC-12 is ounted within. For exa ple, Belden 1120A has a 600v insulation rating and can be used in
any applications. Check with your electrical installer for details as local code require ents ay vary.
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Step 5 – (optional) Connect the 4-20 A input sensor.
The A90DC-12 supports use of both 2 wire and 3 wire 4-20 A sensors as shown in the wiring diagra s above. Note,
the current draw of the 3 wire sensor ust not exceed 200 A. The power consu ed by the sensor ust be added to
the 24VDC power supply require ents. Note: a 24VDC supply ust be used when using the sensor input. (using a 9vdc
supply with the sensor enabled will report an error in the sensor's odbus registers.)
WARNING: After wiring the Power, Analog Input and RS485 cable, remove all scraps of wire or foil shield
from the electrical panel. This could be dangerous if wire scraps come into contact with high voltage wires.
The RS232 connector is provided for fir ware updates only. The RS232 connector ust not be attached to anything while
the A90DC-12 is used in nor al operation.
Step 6 - Power-up the A90DC-12. Observe the LEDs to confir the device is operating.
●Alive (green): blinks once per second while the syste is operating correctly.
●RS485 RX: The RX led should blink whenever a odbus query is sent on the RS485 loop. (regardless of
the target address of the query). If the A90DC-12 is attached to an AcquiSuite or a ModHopper device,
the RX led should blink about once per second.
●RS485 TX: The TX LED will blink when the A90DC-12 responds to a odbus query.
Step 7 - Set the Modbus Address. The default Modbus address of the A90DC-12 is set at the factory between 1 and 128,
and is printed on the product packaging label. If other A90DC-12 devices are to be used in the syste , you ust verify the
Modbus address on each is unique one to prevent two devices fro having the sa e address.
A Modbus aster device or software package is required to configure options on the A90DC-12 as well as read the output
data. The Obvius Config Console software (free at www.obvius.co ) can be used to configure the A90DC-12 Modbus
address or confir readings fro the device. Use the OCC tool to scan for the A90DC-12 if the Modbus Address is not
known.
If you are using software or a PLC to co unicate with the A90DC-12, write the address value to Modbus register 41010.
The address ust be between 1 and 247.
If you are using an AcquiSuite Data Acquisition Server, use your web browser to view the AcquiSuite configuration
webpage. Locate the A90DC-12 in the Modbus Device List. Click on the device in the list to view the details for the
A90DC-12. Next, click the configure button at the botto of the page, and then the “Advanced” button at the botto of the
configuration page.
The Advanced configuration button will display a nu ber of para eters for the A90DC-12. One option is the Modbus
address. Set the required Modbus address (1-247) and click the save button at the botto of the page.
Return to the Modbus device list page. It ay take several inutes for the AcquiSuite to locate the new address for the
device and for the A90DC-12 to appear on the list again. Once it does, click the device and configure a logical na e to
identify the device in the list.
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Step 8 - Once the A90DC-12 is powered up and co unications have been confir ed, the DC load wires should be
installed. Re ove power fro the A90DC-12 before installing the load wires.
WARNING: Disconnect power and lock-out all power sources during installation.
DO NOT CONNECT VOLTAGE OR CURRENT INPUTS LIVE
Each DC load wire should be run through the opening in the A90DC-12 hall effect sensor. The I+ and I- on the side of the
sensor indicates the direction of current flow. The I+ (label side) should point in the direction of the load. In a solar PV
syste , the I+ should point towards the inverter.
This illustration shows the 6 of 12 load wires passing through the individual hall effect sensors. The channel nu ber for
each load wire is shown at the top.
WARNING: The DC load wire that passes through the hall effect sensor opening ust be of sufficient thickness to
prevent the wire fro getting war due to current flow. Refer to local electrical codes for specific wire size
require ents. The DC Load Wire ust not ake any electrical connection to the A90DC-12. Insulated or non-insulated
wire ay be used depending on the application (see specifications page for details). It should only pass through the hall
effect sensor opening.
When installing the load wire, do not pull on, or otherwise stress the hall effect sensors.
Step 9: power up the A90DC-12 and the load wires and confir the readings atch the expected current flow.
Note: If cleaning is required, use a dry towel to re ove dust fro the A90DC-12. Do not use fluids to clean the A90DC-12.
emperature
The A90DC-12 series current onitor is capable of operating within a wide te perature range. Cooling or air circulation
for the A90DC-12 should not be required as long as the a bient air around the device does not exceed the stated li itations
of the product. The power consu ption of the A90DC-12 is relatively stable across all current easure ent ranges so it
does not produce additional heat at high current easure ent ranges.
Note: A bient Air te perature refers to the air i ediately surrounding the A90DC-12. This is not the outdoor air
te perature. The enclosure that the A90DC-12 is ounted inside ay retain so e heat and cause the a bient air
te perature to be hotter than the surrounding outdoor air te perature.
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Monitoring sage:
The A90DC-12 has several data points that ay be read using the Modbus protocol.
For each input channel 1 through 12, the A90DC-12 reports a value for the instantaneous and long average current. The
instantaneous value is co puted using ultiple sa ples of the input channel, averaged together. The instantaneous value
will represent an average sa pling period not longer than 1s. The long average value is co puted by averaging the
instantaneous values together over several inutes (or hours) of ti e. The long average should be cleared by writing a zero
to Modbus register 41017. The long average can accu ulate ore than 30 days worth of average value, however it is not
stored when the power is re oved fro the A90DC-12.
The A90DC-12 also co putes several syste wide values including a total and average value for all channels. For each of
these, both an instantaneous and long average value is reported. Total instantaneous current is the su of the instantaneous
values for all 12 channels. If any channels are disabled, the current value for the channel is not included in the totals.
When using the A90DC-12 with the AcquiSuite data acquisition server, the following configuration page will be presented.
The AcquiSuite will display will report all the data values present on the A90DC-12. In addition, the long average value will
be cleared after each logging interval. Also provided in the AcquiSuite display is the power supply voltage, and onboard
pcb te perature. Lastly, the alar channel will report which channel (if any) are in alar state based on the failure criteria
set up in the advanced configuration page.
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Modb s Feat res
Supported Modbus Functions
The A90DC-12 device responds to the following Modbus query functions:
0x11 Report slave id.
0x03 read holding registers ( ultiple)
0x06 preset single register
These should be sufficient to perfor all operations (read any values, ake single change, and identify). In addition the
device will respond to with Modbus exceptions for invalid function, value, and register if out of bound requests are ade.
Modbus function 0x11 Slave ID response should report the following:
"Obvius, A90DC-12, DC Current Sensor, 12 channel", id=46
"Obvius, A90DC-10, DC Current Sensor, 10 channel", id=46
Modbus Register List
All odbus registers are read-only unless otherwise noted.
Data points: (all read-only)
------- ------- ------- ------------------
offset point type description
0 40001 INT32 MSW total current, Instantaneous AMPS 100, (sum of 12 channels)
1 40002 - LSW total current, Instantaneous AMPS 100, eg 1234 = 12.34A
2 40003 INT32 MSW total current, long average AMPS 100 (sum of 12 channels)
3 40004 - LSW total current, long average AMPS 100 eg 1234 = 12.34A
4 40005 INT16 average current, Instantaneous AMPS 100 (average of 12 channels),
eg 1234 = 12.34A
5 40006 INT16 average current, long average AMPS 100 (average of 12 channels),
eg 1234 = 12.34A
6 40007 UINT16 Alarm Channel: 0=no-alarm,
0xFFFF=invalid, No alarm
1-12=range alarm channel
102=internal positive powersupply bad (+5V)
103=power input over voltage
104=power input under voltage
105=Internal reference powersupply bad. (+2.5V)
106=Current overrange. +/-16A on any channel.
7 40008 UINT16 Alarm Time: 0=no-alarm, 0xFFFF=invalid, 1-65534=number of seconds
that alarm average has been in effect.
8 40009 INT16 PCB temperature, in degrees F, x 100, eg 12345 = 123.45 deg F
9 40010 UINT16 Input power supply, volts x 100. eg 2345 = 23.45v
10 40011 INT16 channel 1 current, Instantaneous AMPS 100
11 40012 INT16 channel 1 current, long average AMPS 100
12 40013 INT16 channel 2 current, Instantaneous AMPS 100
13 40014 INT16 channel 2 current, long average AMPS 100
14 40015 INT16 channel 3 current, Instantaneous AMPS 100
15 40016 INT16 channel 3 current, long average AMPS 100
16 40017 INT16 channel 4 current, Instantaneous AMPS 100
17 40018 INT16 channel 4 current, long average AMPS 100
18 40019 INT16 channel 5 current, Instantaneous AMPS 100
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19 40020 INT16 channel 5 current, long average AMPS 100
20 40021 INT16 channel 6 current, Instantaneous AMPS 100
21 40022 INT16 channel 6 current, long average AMPS 100
22 40023 INT16 channel 7 current, Instantaneous AMPS 100
23 40024 INT16 channel 7 current, long average AMPS 100
24 40025 INT16 channel 8 current, Instantaneous AMPS 100
25 40026 INT16 channel 8 current, long average AMPS 100
26 40027 INT16 channel 9 current, Instantaneous AMPS 100
27 40028 INT16 channel 9 current, long average AMPS 100
28 40029 INT16 channel 10 current, Instantaneous AMPS 100
29 40030 INT16 channel 10 current, long average AMPS 100
30 40031 INT16 channel 11 current, Instantaneous AMPS 100
31 40032 INT16 channel 11 current, long average AMPS 100
32 40033 INT16 channel 12 current, Instantaneous AMPS 100
33 40034 INT16 channel 12 current, long average AMPS 100
34 40035 INT16 reserved
35 40036 INT16 reserved
36 40037 INT16 reserved
37 40038 INT16 reserved
38 40039 INT16 reserved
39 40040 INT16 reserved
40 40041 INT16 reserved
41 40042 INT16 reserved
Analog input Mode setting options. See below for value details.
42 40043 UINT16 reserved
43 40044 UINT16 input broken wire alarm bitmap (1=broken wire, 0=not broken;
bit0=input1.).
offset point type desc modes--> mA
44 40045 UINT16 input 1 mode (NV/r/w)
45 40046 UINT32 input 1 value MSW inst
46 40047 - input 1 value LSW
47 40048 UINT32 input 1 ave MSW ave
48 40049 - input 1 ave LSW
49 40050 UINT32 input 1 min MSW min
50 40051 - input 1 min LSW
51 40052 UINT32 input 1 max MSW max
52 40053 - input 1 max LSW
MODE options for each analog input:
0 = unconfigured (return 0xFFFF for all registers associated with this input)
2 = Analog current mode, 4-20mA range.
System information points:
------- ------- ------- ----- --------------------
offset point type rw/ro desc
1000 41001 UINT16 ro Serial Number (bytes 1,2)
1001 41002 UINT16 ro Serial Number (bytes 3,4)
1002 41003 UINT16 ro Serial Number (bytes 5,6)
1003 41004 UINT16 ro firmware version major
1004 41005 UINT16 ro firmware version minor
1005 41006 UINT16 ro mfg date MSW
1006 41007 UINT16 ro mfg date LSW
1007 41008 UINT16 ro up time (seconds) MSW.
1008 41009 UINT16 ro up time (seconds) LSW.
1009 41010 UINT16 rw/nv Our Modbus address (1-247)
1010 41011 UINT16 ro Hardware Version (0x9012, 0x9010...)
1011 41012 UINT16 ro PCB Rev (0=rev A, etc) (low byte Part Rev)
1012 41013 UINT16 rw/nv Minimum current threshold for alarm feature, amps 100.
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eg 1234 = 12.34A (x100, 0 to 50 amps)
1013 41014 UINT16 rw/nv deviation threshold for alarm feature, percent 100.
eg 1234 = 12.34% (0 to 100%)
1014 41015 UINT16 rw/nv deviation minimum time for alarm feature, in seconds.
(0 to 3600 seconds)
1015 41016 UINT16 rw/nv Channel disable: Bitmap of channels to disable
(0x00 = all 12 enabled, 12 bit: 0x00 to 0xFFF)
1016 41017 UINT16 w Ave-clear: write any value to clear long average.
(read returns zero)
1017 41018 INT16 ro reserved
1018 41019 INT16 ro reserved
1019 41020 UINT16 ro reason for reboot. 0x01=POR, 0x02=EXTR 0x04=WDTR 0x08=BODR,
0x8000=WDTOF
1020 41021 INT16 ro Powersupply, +5v rail. (x100, eg 567 = 5.67v)
1021 41022 INT16 ro reserved
1022 41023 UINT16 ro number of available current channels on system.
A90DC-12 = 12.
Use for register 41016 to find maximum bits allowed.
1023 41024 UINT16 ro number of available analog input channels on the system
(A90DC-12 = 1)
1024 41025 UINT32 ro MSW bitmap of available analog input modes.
1025 41026 -- LSW
0x0002 = Analog 4-20mA mode (only one mode supported)
1026 41027 UINT16 rw/nv Data polarity of current readings: Normal = 1, Inverted = 0.
It effects all instantaneous and long averages, Reg. #40001-
40006, and #40011-40034.
Analog input: Current Mode:
instantaneous: The instantaneous reading will report the present status of the input, represented in oh s, A, or volts. The
value uses a short ter average of the last 16 a/d converter readings to co pute the value of this register. In voltage and
current ode, the instantaneous value is calculated several ti es per second. In resistance ode, the value is calculated at
least every two seconds. 0xFFFFFFFF will report an off-scale-high condition, or any other invalid data.
average: This register reports the longer ter average of the input. Each ti e a short ter average is calculated with all-new
sa ples, the value is added to the cu ulative average. This value should be reset using the clear in/ ax register at least
once per hour. If not cleared, it will eventually start a oving average after e ory storage is exceeded. The AcquiSuite
will clear this register a the start of each data logging period.
min: the ini u value seen in the instantaneous register.
max: the axi u value seen in the instantaneous register.
Multipliers: The register value for inst, average, in, and ax ust be divided by 1000 to convert the nu ber to A.
Current ode reports 0 to 20.000 A.
clear in/ ax (register 41017): This register clears the values for average, in, and ax. The historical accu ulation of
sa ples for the average field will be cleared, and average, in, ax will be set to the present instantaneous value after the
next instantaneous value is recalculated.
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Register formatting
The Modbus data register set includes both 16 and 32 bit values, as well as signed and unsigned nu bers. On Modbus
syste s that do not allow you to read 32bit values, you can calculate the pulse count as follows:
Total = (MSW * 65536) + LSW
When using C or other progra ing languages, you can co bine the with bit shifting and xor.
Total = (MSW << 16) | LSW;
It is i portant to read both the MSW and LSW values in a single Modbus read request. Use the Modbus function 0x03 to
read all the Modbus data registers in a single block, and then asse ble the data point values fro the Modbus registers
received in the query. If the MSW and LSW values are read in separate queries, the value ay be updated between Modbus
queries and the resulting co bined nu ber ay be incorrect.
Data points such as the total and per-channel current easure ents are provided as signed values to represent both positive
and negative current flow. A positive value represents current flow in the direction of the arrow on the top of the hall effect
sensor. Signed values are encoded in standard two's co pli ent for at.
As a general rule, disabled or ax scale current channel register values are for atted with a MAXINT16 or MAXINT32
value depending on whether the register is 16 or 32 bit respectively. This rule applies for all of the individual current
easuring channels 1-12, the total current and average current sets including instantaneous and average values. The
Modbus register point ap described earlier defines the entire Modbus ap for the device.
Alarm configuration
The A90DC-12 provides features to detect alar conditions related to Solar PV applications. For exa ple, in a PV array,
the syste ay have 10 pv panels wired in series per string, and 12 strings that run back to a co biner box. The A90DC-12
can be installed at the co biner box to onitor the current levels on all 12 strings at the sa e ti e. If a panel in one of the
strings fails, the A90DC-12 can detect the reduction in current fro the failed string and set an alar flag to indicate the
proble .
To configure the A90DC-12 to detect this fault condition, several options ust be configured. These options include the
following:
●Deviation threshold.
●Mini u current threshold.
●Mini u deviation ti e for alar .
The first ite to do is calculate what level you need to detect. If you have 10 panels in series and one fails, there should be a
10% reduction in power production. The deviation threshold should be set less than but close to 10%. A good starting
point will be 7%, and then adjust the set point after the syste has so e working data to review.
The second ite is the ini u current threshold. In a solar PV syste , the total current produced varies throughout the
day. At sunrise and sunset, the a ount of power produced is ini al. The ini u level at which the A90DC-12 can
detect current is 0.75A, so the differences between channels will be below the ability of the A90DC-12 to detect. To prevent
this, the ini u current threshold option sets the point at which current levels ust reach in order to enable the alar
feature. If the ini u current threshold is set to 4 a ps, the alar feature will beco e operational when the average
current per channel level exceeds 4 a ps. A good value to set for this option is the axi u current expected, less 10%.
This will allow the average to exceed the ini u current threshold even if one channel fails co pletely.
The third feature that you ust set is the ini u deviation ti e for alar . This feature allows you to select the period of
ti e which the alar ust be in effect before it is reported. This will help suppress transient alar s when brief proble s
occur such as shadows fro a truck or plane are present on one or ore panels in a single string.
Page 14 A90DC-12 – DC Current Monitor
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Mechanical Drawings
The A90DC-12 ust be ounted inside an appropriate enclosure rated for the weather, location, and electrical co ponents
located inside it. The A90DC-12 ounting holes are detailed below.
Page 15 A90DC-12 – DC Current Monitor
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A90DC-12 Firmware Update
Fro ti e to ti e, Obvius ay release fir ware updates with additional features and syste changes. To find out what
fir ware your A90DC-12 has installed, read the fir ware version register with a Modbus utility, or use the “Advanced
configuration” page in the AcquiSuite setup enu. Fir ware update files ay be obtained fro Obvius technical support.
The fir ware update process requires an RS232 serial port and a windows co puter to run the fir ware update utility.
Before starting this process, verify your co puter has a serial port available. You ay need to deactivate other software
such as the pal pilot utility or ups onitor software. USB connected serial ports ay be used, however these are not as fast
or reliable as standard co puter serial ports and ay fail to upgrade the fir ware correctly.
To update the fir ware, use the following procedure.
Step 1: Install the Philips LPC2000 software as provided by Obvius.
Step 2: Re ove power and DC load current fro the A90DC-12. Power can be disconnected by re oving the screw
ter inal plug fro the A90DC-12 power connection socket.
WARNING: Disconnect power and lock-out all power sources during installation.
DO NOT CONNECT RS2 2 PORT WITH CURRENT INPUTS LIVE
Step : Attach the A90DC-12 to your co puter with an RS232 serial cable. The A90DC-12 progra ing connector is the
9 pin RS232 connector on the label side of the device.
Step 4: Power up the 24vdc supply to the A90DC-12. The Green Alive LED should light up and blink.
Step 5: Run the LPC2000 Flash Utility. The following screen will be displayed.
Step 6: Set the following co unications options:
COM1 or COM2 depending on your co puter serial port.
Use baud rate: 38400 or slower.
Check “Use DTR/RTS for Reset”
XTAL Freq[kHz] = 14745
Step 7: Click the “Read Device ID” button. The PartID and BootLoaderID fields will be shown if successful. Also, the
“Device” dropdown enu should switch to LPC2132. The botto of the window will display “Read Part ID Successfully.”
Step 8: Click the “Filena e” “...” button. A dialog box will appear. Locate and select the A90DC-12 fir ware i age file.
In the exa ple above, this is na ed “A90DC-12_v1.25.hex”.
Step 9: Click the “Erase” button. This will re ove the existing fir ware fro the A90DC-12 device.
Step 10: Click the “Upload to Flash” button. The fir ware update will start, and a blue progress bar will be shown across
the botto of the screen. While the upload is in progress, the green Alive LED on the A90DC-12 will stop blinking and
stay on solid.
Step 11: when the update is co plete, disconnect power fro the A90DC-12. Re ove the RS232 serial cable.
Step 12: Re-attach the data and load wire connections. Power up the A90DC-12. The new fir ware should now operate.
To confir the new fir ware is installed, use the AcquiSuite device details page, click the “configure” button, and then the
“Advanced” button. The fir ware version nu ber will be displayed on the upper right side of the advanced details page.
Page 16 A90DC-12 – DC Current Monitor
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