Obvius A90DC-12, A90DC-10 Installation And Operation Manual

A90DC-12 – DC Current Monitor

Obvius, LLC

Installation and Operation Manual

Model A90DC-12, A90DC-10

Date: Sep 4, 2013

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Copyright Information

Copyright © 2007 - 2013 by Obvius

Obvius, AcquiSuite and ModHopper are trademarks of Obvius Holdings LLC

Other brand and product names are trademarks or registered trademarks of their respective holders.

U.S. Government Restricted Rights: Use, duplication or disclosure by the Government is subject to restrictions set fourth in subparagraph (a) through
(d) of the Commercial Computer Restricted Rights clause at FAR 52.227-19 when applicable, or subparagraph (c) (1) (ii) of the Rights in Technical Data
and Computer Software clause at DFARS 252.227-7013, and in similar clauses in the NASA FAR Supplement.

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 promises buyer that any standard product manufactured by Obvius shall be free from all material defects in design, material, or manufacturing for
a period of 2 years from the manufacture date; provided, however, that the warranty shall not extend to ordinary wear and tear or to normally replaceable
components (e.g., batteries). During the warranty period, Obvius may repair or replace (in its sole discretion) any product suffering from a warranty defect
and returned freight prepaid by buyer, with no charge to buyer for any warranty repair or replacement. The warranty shall remain in full force and effect
for such 2 year period, provided that the product: (1) was installed, operated, and maintained properly; (2) has not been abused or misused; (3) has not
been repaired, altered, or modified outside of Obvius's authorized facilities; (4) has not been sold subject to other warranty terms specified at the time of
sale; and (5) is still owned by the original purchaser. This warranty provides specific legal rights that may be varied by state law. Obvius's products are not
designed for life or safety applications.

Product Application Limitation

Obvius strongly believes in continuous improvement, therefore we must 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 Symbols:...............................................................................................................................................................3

Overview......................................................................................................................................................................................4

Applications.................................................................................................................................................................................4

Installation Checklist...................................................................................................................................................................4

Hardware Overview.....................................................................................................................................................................5

A90DC-12, A90DC-10 Series Features and Specifications...................................................................................................5

Power and Communication Connections...............................................................................................................................6

Hardware Installation.............................................................................................................................................................6

Temperature...........................................................................................................................................................................8

Monitoring usage:........................................................................................................................................................................9

AcquiSuite Advanced Configuration Options................................................................................................................10

Modbus Features........................................................................................................................................................................11

Supported Modbus Functions..............................................................................................................................................11

Modbus Register List...........................................................................................................................................................11

Register formatting.........................................................................................................................................................14

Alarm configuration.......................................................................................................................................................14

Mechanical Drawings................................................................................................................................................................15

A90DC-12 Firmware Update.....................................................................................................................................................16

Markings and Symbols:

WARNING: A potential risk exists if the operating instructions are not followed

General Warning Symbol: This symbol indicates the need to consult the operating instructions provided with the
product.

This symbol indicates the presence of electric shock hazards.

This symbol indicates: Do not apply to or remove from hazardous live conductors.

Direct Current symbol.

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Overview

The A90DC-12 DC Series current monitor system is designed to allow measurement and alarming of DC current
applications including solar pv arrays, battery monitoring and DC power supplies for telecom switch gear.

The A90DC-12 uses 12 non-contact DC Hall Effect sensors to measure DC current on each of the 12 channels. DC current
can be measured in both directions, showing positive and negative numbers in the resulting measurement values. Data
values are made 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 alarm functions to monitor
imbalances between channels. This feature is instrumental in detecting failed equipment 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 monitoring.

Installation Checklist

An A90DC-12 system installation has the following components:

Required hardware

● A90DC-12 Series DC current monitor (required)

● 24VDC power supply

● Data connection to a Modbus master device such as an AcquiSuite, ModHopper, PLC or computer software such as

the Obvius Config Console.

● Enclosure for the A90DC-12 DC to satisfy UL safety requirements.

● Shielded twisted pair wire for communications.

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 computer.

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Hardware Overview

A90DC-12, A90DC-10 Series Features and Specifications

Processor Arm7 embedded CPU
LED Alive (green), RS485 TX, RX (yellow)
Protocol Modbus RTU
Addressing Modbus address may be set from 1 to 247 via Modbus register.
Power Supply Power input : 9-30vdc at 1.25W. (power supply not included)

140mA typical at 9vdc, 55mA typical at 24vdc. (excluding the 4-20mA sensor input channel)
Note: 24vdc required for use of the 4-20mA analog input port. When fully loaded, the maximum
current should not exceed 250mA.
Transient overvoltage rating 1500V

Current Inputs

Accuracy: +/- 5% of full scale (+/- 0.75A) at 25ºc
Analog input1: 4-20mA analog input:
Measurements DC current per channel, instantaneous and average

Alarming Low alarm may set as a percent of DC average of other channels.

Communications1RS-485 (+,-, S), 9600 baud, N, 8, 1, two wire. Supports up to 32 external devices (expandable)
Isolation The RS485 terminals electrically isolated to 1500V from the remainder of the A90DC-12 board.
Environmental

Safety UL61010 Recognized

EMC FCC CFR 47 Part 15, Class A
Size 12.85” x 2.5” x 1.75” (326mm x 64mm x 45mm)
Mass 0.83 lbs (0.375 kg)

2

12 DC Hall Effect Sensors, non-contact.
Maximum range +15Amps to -15Amps DC
The product is intended to measure 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.

Total DC current (sum of 12 channels), instantaneous and average
Average DC current (of 12 channels), instantaneous and average

Alarms may be disabled below a minimum average current level.
Minimum time for alarm may be set to prevent alarms on brief events.
Unused channels may be disabled to exclude them from total and average calculations.

2

North America: Temperature -30º – 70ºc, 0 – 95% humidity, non-condensing.
Altitude up to 2000M.
For indoor and outdoor use when used in an appropriate enclosure.
The A90DC-12 must be mounted inside a NEMA rated electrical enclosure for safety and isolation
requirements.

File: E320540 (Model3 A90DC-12, A90DC-10)

Measurement 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 must be rated to 1000v)

1

Outputs are intended for low voltage class 2 inputs.

2

If the product is used in a manner not specified by the manufacture, the protection provided by the equipment may be

impaired.

3

Note: The A90DC-12 or A90DC-10 models are identical except for the number of DC current sensor channels present on
the device. This manual will refer to model A90DC-12 however the manual covers installation and operation for all three
models except where otherwise noted.

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Power and Communication Connections

Hardware Installation

Step 1 - Unpack materials: Remove all materials from shipping box and verify all required components are available

Step 2 - Mount the A90DC-12 inside the electrical enclosure. Be sure to provide enough room to route the load wires

through the hall effect sensor openings.

Step 3 – Attach the power supply to the A90DC-12. Be sure to observe the polarity. Note: Power can be
disconnected by removing the screw terminal plug from 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 diagram. Follow the manufacturer’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 same address). Connect each device in the chain by “daisy-chaining” the devices together .
Observe + and - polarity on the Modbus devices. For more information 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 mechanically secured where it enters the electrical panel.

The wire used to provide RS485 communications should be insulated to meet requirements of the voltages present inside the
box that the A90DC-12 is mounted within. For example, Belden 1120A has a 600v insulation rating and can be used in
many applications. Check with your electrical installer for details as local code requirements may vary.

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Step 5 – (optional) Connect the 4-20mA input sensor.

The A90DC-12 supports use of both 2 wire and 3 wire 4-20mA sensors as shown in the wiring diagrams above. Note,

the current draw of the 3 wire sensor must not exceed 200mA. The power consumed by the sensor must be added to
the 24VDC power supply requirements. Note: a 24VDC supply must be used when using the sensor input. (using a 9vdc
supply with the sensor enabled will report an error in the sensor's modbus 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 firmware updates only. The RS232 connector must not be attached to anything while
the A90DC-12 is used in normal operation.

Step 6 - Power-up the A90DC-12. Observe the LEDs to confirm the device is operating.

● Alive (green): blinks once per second while the system is operating correctly.

● RS485 RX: The RX led should blink whenever a modbus 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 modbus 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 system, you must verify the
Modbus address on each is unique one to prevent two devices from having the same address.

A Modbus master 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.com) can be used to configure the A90DC-12 Modbus
address or confirm readings from 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 communicate with the A90DC-12, write the address value to Modbus register 41010.
The address must 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 bottom of the page, and then the “Advanced” button at the bottom of the
configuration page.

The Advanced configuration button will display a number of parameters for the A90DC-12. One option is the Modbus
address. Set the required Modbus address (1-247) and click the save button at the bottom of the page.

Return to the Modbus device list page. It may take several minutes 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 name to
identify the device in the list.

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Step 8 - Once the A90DC-12 is powered up and communications have been confirmed, the DC load wires should be
installed. Remove power from 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
system, 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 number for
each load wire is shown at the top.

WARNING: The DC load wire that passes through the hall effect sensor opening must be of sufficient thickness to

prevent the wire from getting warm due to current flow. Refer to local electrical codes for specific wire size
requirements. The DC Load Wire must not make any electrical connection to the A90DC-12. Insulated or non-insulated
wire may 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 confirm the readings match the expected current flow.

Note: If cleaning is required, use a dry towel to remove dust from the A90DC-12. Do not use fluids to clean the A90DC-12.

Temperature

The A90DC-12 series current monitor is capable of operating within a wide temperature range. Cooling or air circulation
for the A90DC-12 should not be required as long as the ambient air around the device does not exceed the stated limitations
of the product. The power consumption of the A90DC-12 is relatively stable across all current measurement ranges so it
does not produce additional heat at high current measurement ranges.

Note: Ambient Air temperature refers to the air immediately surrounding the A90DC-12. This is not the outdoor air
temperature. The enclosure that the A90DC-12 is mounted inside may retain some heat and cause the ambient air
temperature to be hotter than the surrounding outdoor air temperature.

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Monitoring usage:

The A90DC-12 has several data points that may 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 computed using multiple samples of the input channel, averaged together. The instantaneous value
will represent an average sampling period not longer than 1s. The long average value is computed by averaging the
instantaneous values together over several minutes (or hours) of time. The long average should be cleared by writing a zero
to Modbus register 41017. The long average can accumulate more than 30 days worth of average value, however it is not
stored when the power is removed from the A90DC-12.

The A90DC-12 also computes several system 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 sum 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 temperature. Lastly, the alarm channel will report which channel (if any) are in alarm state based on the failure criteria
set up in the advanced configuration page.

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Modbus Features

Supported Modbus Functions

The A90DC-12 device responds to the following Modbus query functions:

0x11 Report slave id.

0x03 read holding registers (multiple)

0x06 preset single register

These should be sufficient to perform all operations (read many values, make 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 made.

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 modbus 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),

5 40006 INT16 average current, long average AMPS * 100 (average of 12 channels),

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

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

eg 1234 = 12.34A

eg 1234 = 12.34A

that alarm average has been in effect.

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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.

1014 41015 UINT16 rw/nv deviation minimum time for alarm feature, in seconds.

1015 41016 UINT16 rw/nv Channel disable: Bitmap of channels to disable

1016 41017 UINT16 w Ave-clear: write any value to clear long average.

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,

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.

1023 41024 UINT16 ro number of available analog input channels on the system

1024 41025 UINT32 ro MSW bitmap of available analog input modes.
1025 41026 -- LSW

1026 41027 UINT16 rw/nv Data polarity of current readings: Normal = 1, Inverted = 0.

eg 1234 = 12.34% (0 to 100%)

(0 to 3600 seconds)

(0x00 = all 12 enabled, 12 bit: 0x00 to 0xFFF)

(read returns zero)

0x8000=WDTOF

A90DC-12 = 12.
Use for register 41016 to find maximum bits allowed.

(A90DC-12 = 1)

0x0002 = Analog 4-20mA mode (only one mode supported)

It effects all instantaneous and long averages, Reg. #40001­40006, and #40011-40034.

Analog input: Current Mode:

instantaneous: The instantaneous reading will report the present status of the input, represented in ohms, mA, or volts. The

value uses a short term average of the last 16 a/d converter readings to compute the value of this register. In voltage and
current mode, the instantaneous value is calculated several times per second. In resistance mode, 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 term average of the input. Each time a short term average is calculated with all-new
samples, the value is added to the cumulative average. This value should be reset using the clear min/max register at least
once per hour. If not cleared, it will eventually start a moving average after memory storage is exceeded. The AcquiSuite
will clear this register a the start of each data logging period.

min: the minimum value seen in the instantaneous register.

max: the maximum value seen in the instantaneous register.

Multipliers: The register value for inst, average, min, and max must be divided by 1000 to convert the number to mA.

Current mode reports 0 to 20.000mA.

clear min/max (register 41017): This register clears the values for average, min, and max. The historical accumulation of
samples for the average field will be cleared, and average, min, max 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 numbers. On Modbus
systems 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 programming languages, you can combine them with bit shifting and xor.

Total = (MSW << 16) | LSW;

It is important 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 assemble the data point values from the Modbus registers
received in the query. If the MSW and LSW values are read in separate queries, the value may be updated between Modbus
queries and the resulting combined number may be incorrect.

Data points such as the total and per-channel current measurements 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 compliment format.

As a general rule, disabled or max scale current channel register values are formatted 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
measuring channels 1-12, the total current and average current sets including instantaneous and average values. The
Modbus register point map described earlier defines the entire Modbus map for the device.

Alarm configuration

The A90DC-12 provides features to detect alarm conditions related to Solar PV applications. For example, in a PV array,
the system may have 10 pv panels wired in series per string, and 12 strings that run back to a combiner box. The A90DC-12
can be installed at the combiner box to monitor the current levels on all 12 strings at the same time. If a panel in one of the
strings fails, the A90DC-12 can detect the reduction in current from the failed string and set an alarm flag to indicate the
problem.

To configure the A90DC-12 to detect this fault condition, several options must be configured. These options include the
following:

● Deviation threshold.

● Minimum current threshold.

● Minimum deviation time for alarm.

The first item 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 system has some working data to review.

The second item is the minimum current threshold. In a solar PV system, the total current produced varies throughout the
day. At sunrise and sunset, the amount of power produced is minimal. The minimum 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 minimum current threshold option sets the point at which current levels must reach in order to enable the alarm
feature. If the minimum current threshold is set to 4 amps, the alarm feature will become operational when the average
current per channel level exceeds 4 amps. A good value to set for this option is the maximum current expected, less 10%.
This will allow the average to exceed the minimum current threshold even if one channel fails completely.

The third feature that you must set is the minimum deviation time for alarm. This feature allows you to select the period of
time which the alarm must be in effect before it is reported. This will help suppress transient alarms when brief problems
occur such as shadows from a truck or plane are present on one or more panels in a single string.

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Mechanical Drawings

The A90DC-12 must be mounted inside an appropriate enclosure rated for the weather, location, and electrical components
located inside it. The A90DC-12 mounting holes are detailed below.

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A90DC-12 Firmware Update

From time to time, Obvius may release firmware updates with additional features and system changes. To find out what
firmware your A90DC-12 has installed, read the firmware version register with a Modbus utility, or use the “Advanced
configuration” page in the AcquiSuite setup menu. Firmware update files may be obtained from Obvius technical support.

The firmware update process requires an RS232 serial port and a windows computer to run the firmware update utility.
Before starting this process, verify your computer has a serial port available. You may need to deactivate other software
such as the palm pilot utility or ups monitor software. USB connected serial ports may be used, however these are not as fast
or reliable as standard computer serial ports and may fail to upgrade the firmware correctly.

To update the firmware, use the following procedure.

Step 1: Install the Philips LPC2000 software as provided by Obvius.

Step 2: Remove power and DC load current from the A90DC-12. Power can be disconnected by removing the screw

terminal plug from the A90DC-12 power connection socket.

WARNING: Disconnect power and lock-out all power sources during installation.
DO NOT CONNECT RS232 PORT WITH CURRENT INPUTS LIVE

Step 3: Attach the A90DC-12 to your computer with an RS232 serial cable. The A90DC-12 programming 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 communications options:

COM1 or COM2 depending on your computer 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 menu should switch to LPC2132. The bottom of the window will display “Read Part ID Successfully.”

Step 8: Click the “Filename” “...” button. A dialog box will appear. Locate and select the A90DC-12 firmware image file.
In the example above, this is named “A90DC-12_v1.25.hex”.

Step 9: Click the “Erase” button. This will remove the existing firmware from the A90DC-12 device.

Step 10: Click the “Upload to Flash” button. The firmware update will start, and a blue progress bar will be shown across

the bottom 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 complete, disconnect power from the A90DC-12. Remove the RS232 serial cable.

Step 12: Re-attach the data and load wire connections. Power up the A90DC-12. The new firmware should now operate.

To confirm the new firmware is installed, use the AcquiSuite device details page, click the “configure” button, and then the
“Advanced” button. The firmware version number will be displayed on the upper right side of the advanced details page.

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