Observator Instruments OMC-183-ML User manual

OMC-183-ML Signal Conditioning Unit
Installation & technical user manual
Version 1.05 - 2019
Author: Observator Instruments

OMC-183-ML Manual Page 2
Revisions:
0.1 (26-08-2016) Conversion of OMC-183 hardware into OMC-183-ML hardware
Original OMC-183 manual version 3.17 was used to create this
installation & technical user manual
0.2(26-09-2016) Review version
1.01 (25-10-2016) First release
1.02 (24-9-2018) Correction in connection OMC-938 display (page 12).
1.03 (15-11-2018) Correction baud rate OMC-2900 output (fixed 4800 like both NMEA
inputs) .
1.04 (4-12-2018) Correction name ‘new OMC-406’to OIC-406
1.05 (8-10-2019) Correction connections OMC-9501 (page 11 chapter 2.9)

OMC-183-ML Manual Page 3
Index
1. INTRODUCTION .................................................................................................................... 5
1.1. INCLUDED TYPES OF OMC-183-ML....................................................................................5
2. INSTALLATION...................................................................................................................... 6
2.1. CONNECTIONS...................................................................................................................7
2.2. OMC-160 WIND SENSORS (NMEA)..................................................................................8
2.3. OMC-116 WIND SENSORS (NMEA)..................................................................................8
2.4. OMC-118 ULTRASONIC WIND SENSOR (RS422 NMEA).....................................................9
2.5. OMC-150/158 EEX WIND SENSOR....................................................................................9
2.6. OIC-406 TEMPERATURE &HUMIDITY SENSOR................................................................. 10
2.7. OMC-406 TEMPERATURE &HUMIDITY SENSOR.............................................................. 10
2.8. OMC-506 SINGLE BAROMETRIC PRESSURE SENSOR.(4-20MA) ....................................... 11
2.9. OMC-9501 BAROMETRIC PRESSURE SENSOR(S). (0 -2.5V /0-5V) ................................. 11
2.10. OMC-443 TEMPERATURE SENSOR (4-20MA) .................................................................. 12
2.11. OMC-938/939 DISPLAY (RS422 /OMC-2900)............................................................... 12
3. COMMISSIONING THE OMC-183-ML................................................................................. 13
3.1. CONNECTING YOUR PC /LAPTOP TO THE OMC-183-ML .................................................. 13
3.2. DEVICE STATUS.............................................................................................................. 13
3.3. USER SETTINGS QNH &QFE ......................................................................................... 14
4. MENU STRUCTURE ............................................................................................................ 15
5. EU DECLARATION OF CONFORMITY .............................................................................. 18

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OMC-183-ML Manual Page 5
1. Introduction
The OMC-183-ML is a signal conditioning unit. It is designed to read and feed multiple sensors
and multiplex these signals to a serial signal. It does not log or store any data. Although the
OMC-183 can be used in many applications, this manual assumes it is used for meteorological
applications.
This manual is intended for qualified engineers with basic electronics knowledge. Usually the
OMC-183-ML is factory configured for your application and no changes besides some optional
user settings are required.
1.1. Included types of OMC-183-ML
In 2016 the hardware of the OMC-183 has been revised and all types of OMC-183 are included
into one hardware design. The following inputs* and outputs are available:
Inputs name
Functionality
0-5Vdc IN 1
Voltage in no.1
0-5Vdc IN 2
Voltage in no.2
0-5Vdc IN 3
Voltage in no.3
0-5Vdc IN 4
Voltage in no.4
0-24mA IN 1
Current in no.1
0-24mA IN 2
Current in no.1
0-24mA IN 3
Current in no.1
NMEA1 IN
Wind sensor 1
NMEA2 IN
Wind sensor 2
Outputs name
Functionality**
NMEA OUT
RS422 with NMEA
NMEA Return
RS422 with OMC-2900 format
RS232 TX
RS232 RX
Used for firmware upgrade,
configuration ***
* 4 analogue inputs of this list can be selected simultaneously as a maximum.
** The functionality of Current Loop (CL) output is no longer present in the new hardware design.
*** For backwards compatibility OMC-2900 is also at RS232 available after changing user
settings.

OMC-183-ML Manual Page 6
2. Installation
The OMC-183-ML is designed to be used indoors. Find a suitable location with the required
power and run your cables for all sensors.
Typically you will find the following sensors:
- wind sensor (OMC-160, OMC-116, OMC-118, OMC-150 or OMC-115)
- temperature & humidity sensor (OMC-406, OMC-443 or OMC-448)
- barometric pressure sensor (OMC-506: preferable build in OMC-183-ML housing*)
Output:
- Observator Display line: OMC-140, OMC-138/139 OMC-938/939
- OMC-data Online / OMC-DOL-HMS
Typical configuration with OMC-160 wind sensor, OMC-406 temperature & humidity sensor &
(dual) barometric pressure sensor.
* The OMC-506 must be vented outside via a tube whenever it is build in the OMC-183 housing and
the room is pressurized. We recommend to use a pressure head OMC-509 at the outdoor end of the
tube.
The OMC-183-ML is the replacement of the OMC-183 and got similar functionality. The additional
connectors are used in the MeteoLink products, some of these connectors may be functional in the
OMC-183-ML but others got a different functionality when compared to the MeteoLink concept.

OMC-183-ML Manual Page 7
2.1. Connections
The in the lid of the casing and on the printed circuit board a description of the functionality of
each pin is given. These descriptions are also used for MeteoLink products, therefore some
functionalities are available in the OMC-183-ML software.
Top row
Pin
Function
Bottom row
Pin
Function
1
GND [SUP] IN
17
GND
2
VIN [12-24VDC] IN
18
SUPPLY
3
NMEA_OUT_A
19
RS232_TX
4
NMEA_OUT_B
20
RS232_RX
5
SHIELD
21
RS485_422_IN_A
6
NMEA_RETURN_A
22
RS485_422_IN_B
7
NMEA_RETURN_B
23
GND
8
SHIELD
24
SUPPLY
9
GND [SUP]
25
0-5VDC_IN_1
10
SUPPLY
26
GND
11
NMEA1_IN_A
27
SUPPLY
12
NMEA1_IN_B
28
0-24mA_IN_1
13
GND [SUP]
29
GND
14
SUPPLY
30
CMOS_SUPPLY
15
NMEA2_IN_A
31
CMOS_TX
16
NMEA2_IN_B
32
CMOS_RX
Top row
Pin
Function
Bottom row
Pin
Function
40
GND
46
GND
41
RAIN_IN
47
SUPPLY
42
GND
48
0-5 V INPUT 2
43
SUPPLY
49
GND
44
RS485_A
50
SUPPLY
45
RS485_B
51
GND
Top row
Pin
Function
Bottom row
Pin
Function
60
0-24 mA INPUT 2
66
0-5 V INPUT 3
61
SUPPLY
67
GND
62
GND
68
SUPPLY
63
0-24 mA INPUT 3
69
0-5 V INPUT 4
64
SUPPLY
70
GND
65
GND
71
SUPPLY

OMC-183-ML Manual Page 8
2.2. OMC-160 Wind sensors (NMEA)
The Cup & Vane wind sensor got a standardized RS-422 output with NMEA protocol.
2 sensors can be connected.
OMC-183-ML
OMC-160
Sensor
1
2
GND [SUP]
9
13
1
Power GND
SUPPLY
10
14
2
Power 12-24V
NMEA1_IN_A
11
15
10
RS422 - out
NMEA1_IN_B
12
16
9
RS422 + out
Recommended cable: shielded 2x2x0,75mm2 twisted pair
OMC-160: NO Jumper on 13 -14
The optional heater will require a separate power supply.
Refer to OMC-160 manual.
2.3. OMC-116 Wind sensors (NMEA)
The Ultrasonic wind sensor got a standardized RS-422 output with NMEA protocol.
2 sensors can be connected.
OMC-183-ML
OMC-116
Sensor
1
2
GND [SUP]
9
13
1
Power GND
SUPPLY
10
14
2
Power 12-24V
NMEA1_IN_A
11
15
4
NMEA 0183 A
NMEA1_IN_B
12
16
3
NMEA 0183 B
Recommended cable: shielded 2x2x0,75mm2 twisted pair

OMC-183-ML Manual Page 9
2.4. OMC-118 Ultrasonic Wind sensor (RS422 NMEA)
Recommended cable: shielded 2x2x0,75mm2 twisted pair
Wires of OMC-118 come in pairs
Take care to use the correct (black) wires.
The junction box is part of the optional
bracket OMC-122(-M).
2.5. OMC-150/158 EEx Wind sensor.
The old OMC-158 is not compatible met the OMC-183-ML, however the new OMC-158-2
contains RS-422 NMEA output signal and is compatible. The wiring is similar to the
OMC-160.
OMC-183-ML
OMC-118
GND [SUP]
13
3
Black
POWER SUPPLY V- (GND)
SUPPLY
14
4
Red
POWER SUPPLY V+ (12-24V)
NMEA1_IN_A
15
5
Black
RS 422 TXA (-)
NMEA1_IN_B
16
6
Green
RS 422 TXB (+)

OMC-183-ML Manual Page 10
2.6. OIC-406 Temperature & Humidity sensor.
The OIC-406 has NMEA output. Connecting the basic node to OMC-183-ML is possible
by using NMEA1 IN or NMEA2 IN.
2.7. OMC-406 Temperature & Humidity sensor.
The old OMC-406 is a less accurate sensor, and got two 4-20mA analog outputs. These
signals can be connected to OMC-183-ML by using two of the analog current input ports
for example current inputs 2 & 3:
Recommended cable: shielded 2x2x0,75mm2 twisted pair
OMC-183-ML
OIC-406 (NMEA)
GND [SUP]
13
1
GND [SUP]
SUPPLY
14
2
SUPPLY
NMEA2_IN_A
15
3
NMEA_OUT_A
NMEA2_IN_B
16
4
NMEA_OUT_B
OMC-183-ML
OMC-406 (4-20mA)
GND
62
Yellow
Power GND
SUPPLY
61
Green
Power +24V
0-24 mA INPUT 2
60
Brown
4-20mA out
(temperature)
0-24 mA INPUT 3
63
White
4-20mA out
(humidity)

OMC-183-ML Manual Page 11
2.8. OMC-506 Single Barometric pressure sensor. (4-20mA)
Recommended cable: shielded 2x0,75mm2 twisted pair
The sensor can be build in the same housing
as the OMC-183-ML
Connections of sensor wires are identical.
2.9. OMC-9501 Barometric pressure sensor(s). (0 - 2.5V / 0 -5V)
OMC-183-ML
OMC-9501
Sensor
1
2
V_IN
66
69
VOUT
V out
GND
67
70
GND
Power GND
AGND
Analogue GND
SUPPLY
68
68
TRIG
Trigger
Supply
Supply
OMC-183-ML
OMC-506
GND [SUP]
26
SUPPLY
27
2
Black
Power 12-24V
0-24mA_IN_1
28
1
White
4-20 mA out

OMC-183-ML Manual Page 12
2.10. OMC-443 Temperature sensor (4-20mA)
Recommended cable: shielded 2x0,75mm2 twisted pair
This type of sensor comes in different versions. They all are loop powered 4-20mA
sensors.
2.11. OMC-938/939 Display (RS422 / OMC-2900)
Recommended cable: shielded 2x0,75mm2 twisted pair
The OMC-938 is usually connected to the RS422 output of the OMC-183-ML.
With the OMC-183-ML it’s no longer optional to use current loop output.
Reconfigure the OMC-938/9 to RS422 if required, see OMC-938/939 manual.
OMC-183-ML
OMC-406 NMEA
SUPPLY
27
Power +24V
0-24 mA INPUT 2
28
4-20mA out
(Air temperature)
OMC-183-ML
OMC-938
GND [SUP]
1
1
POWER SUPPLY V- (GND)
VIN [12-24VDC]
2
2
POWER SUPPLY V+ (12-24V)
NMEA_RTRN_A
6
3
RS 422 TXA (-)
NMEA_RTRN_B
7
4
RS 422 TXB (+)
SHIELD
8

OMC-183-ML Manual Page 13
3. Commissioning the OMC-183-ML
There are two output options, both use one way RS-422 serial communication. One contains the
NMEA data protocol format. The other one got the old OMC-2900 format for backwards
compatibility purposes. To execute analog input calibration and other configuration settings, there
is also a bi-directional RS-232 menu available.
To read the sensors, each unit contains four 0-5 Voltage inputs and three 0-24mA current inputs.
All these analog inputs have already been configured during the manufacturing process.
3.1. Connecting your PC / laptop to the OMC-183-ML
Since most computers don’t have a comport any more, an additional Serial to USB adapter is
needed. Install a terminal program like HyperTerminal, OMC-Terminal, Procomm+, etc. and use
the following settings for the different COM ports.
NO flow control!
3.2. Device status
There are six LED’s on the bottom right corner of the printed circuit board,
they indicate the status of the device. After power-up the orange LED
indicates that the microcontroller is powered. The second LED is red and
indicates a bus overflow, when this LED blinks there is too much data
input to send all incoming messages as output. In this case the device
has to ignore some input messages and information might not be sent as
output and information might get lost.
The other four green LED’s indicate the status of the Serial, NMEA out,
NMEA in 2, NMEA in 1 inputs. When valid messages are received these
LED’s blink. All NMEA messages have to be compliant in order to let de
LED blink. For the serial LED a blink means that a valid RS-485, RS-
232 or other sensor message is received. For each serial sensor a
software driver is included in the device. In order to connect jet unknown
sensors an additional driver and new firmware is needed.
Connector pins
Interface
Default data settings
Baud rate, Data bits, Parity, stop bit
NMEA OUT
1-4
RS-422
4800 (or 9600), 8, N, 1
OMC-2900 OUT
6-7
RS-422
4800, 8, N, 1
Interface
17-20
RS-232
115200 (or 4800/9600), 8, N, 1
If you experience difficulties connecting with the device; Check if the LED’s are blinking, Check the
wiring of the Tx/Rx or A/B wires; Check the data settings of your COM port.
Note: The RJ-45 / Ethernet option is not active on the OMC-183-ML, theses LED’s are switched off.

OMC-183-ML Manual Page 14
3.3. User settings QNH & QFE
Calculation of the QNH & QFE is required when the meteorological station is used for helideck or
runway monitoring. QNH is the barometric pressure at sea level, while QFE is the barometric
pressure at helideck (the same applies for a runway).
For this calculation the height of the helideck above sea level is required as well as the height of
the barometric sensor above the helideck. These values will be negative if they are below sea
level or helideck.
The height of the barometric sensor above the helideck will be set in variable S1, this value will
be negative when the sensor is below the helideck.
The height of the helideck above sea level will be set in variable S2, this value will be negative
when runway is below sea level.
According to the CAP-437 barometric pressure must be measured with a minimum of 2 sensors
placed at the same location. These Dual barometric sensors have been implemented in the
OMC-183-ML according to the CAP-437. One important implementation is output messages:
First when the difference between the two sensors is >0.5 hPa, no data should be presented.
In this case no barometric information messages will be send by the device.
In the OMC-2900 format an additional status message of the Barometric sensors is included:
S0 = Normal operation of dual barometric sensors
S1 = Sensor 1 Error or out of range (threshold settings)
S2 = Sensor 2 Error or out of range (threshold settings)
S3 = Sensor 1 or 2 Error or both out of range (threshold settings)
S4 = Maximum deviation of barometric pressure > default 0.5
Always use the height of the location of the barometric sensor itself, even if a pressure head
(OMC-509) is used. The location of the pressure head is irrelevant for the sensor height!
The sensor is preferable build in the same housing as the OMC-183-ML.

OMC-183-ML Manual Page 15
4. Menu structure
Once the RS-232 connection is established, the command “menu” can be given in the terminal
screen, which will display the following text.
Commands 0-2: The 0-24mA current inputs need to be configured in order to convert the
current value into the right parameter.
The OMC-183-ML will use 2 baro sensors as maximum, do not assign more (either current
or voltage), since this could lead to unpredictable behavior!
Commands 3-6: The 0-5 Voltage inputs need to be configured in order to convert the
voltage into the right parameter.
0: 0-20 mA INPUT 1 (pin 28): [not assigned]
1: 0-20 mA INPUT 2 (pin 60): [4-20 mA Baro sensor (range: 800 - 1100 mB)]
2: 0-20 mA INPUT 3 (pin 63): [4-20 mA Baro sensor (range: 800 - 1100 mB)]
3: 0-5 V INPUT 1 (pin 25): [not assigned]
4: 0-5 V INPUT 2 (pin 48): [not assigned]
5: 0-5 V INPUT 3 (pin 66): [not assigned]
6: 0-5 V INPUT 4 (pin 69): [not assigned]
7: Calculation settings
8: Configure baudrates
9: OMC-2900 Output over RS-232: [ENABLED]
A: Calibrate: 0-24 mA INPUT 2 (pin 60) [CALIBRATED]
B: Calibrate: 0-24 mA INPUT 3 (pin 63) [CALIBRATED]
C: Calibrate: 0-5 V INPUT 3 (pin 66) [CALIBRATED]
D: Calibrate: 0-5 V INPUT 4 (pin 69) [CALIBRATED]
E: Show Analog calibration values
Q: Save and exit menu
0: not assigned
1: 4-20 mA Baro sensor (range: 800 - 1100 mB)
2: 4-20 mA Air temperature sensor (range: -40 - 60 C)
3: 4-20 mA Air temperature sensor (range: -30 - 70 C)
4: 4-20 mA Humidity sensor (range: 0 - 100 %)
0: not assigned
1: 0-5 V Baro sensor (range: 800 - 1100 mB)
2: 0-2,5V Baro sensor (range: 800 - 1100 mB)

OMC-183-ML Manual Page 16
Command 7: Certain parameters are needed in order to calculate the QNH and QFH pressure
and to set the status settings as explained in chapter 3.3.
Command 8: It’s possible to change the baud rate of the serial inputs and outputs. These
settings will only be active after twice the “Q” command and the ‘Save and exit menu’.
Note: When you change RS-232 baud rates, change your terminal settings as well,
change is effective once you leave the menu.
Command 9: It’s possible to use the RS232 as OMC-2900 output as well. Command 9
enables/disables the OMC-2900 over RS-232.
Command A-D: (re)Calibration of the analog inputs can be done by using the commands
A-D. The represented inputs are located on the extension board, therefore they need calibration
after the assembly line. Please make sure calibrated equipment is used to present the right
current or voltage.
If the presented values are way of the expected values the old values of calibration will remain.
Calculation Settings
0: Barometer height above runway (m): -5.00
1: Runway elevation above sea level (m): 10.00
2: Lower threshold barometric pressure (mB): 975.00
3: Upper threshold barometric pressure (mB): 1050.00
4: Maximum deviation barometric pressure (mB): 0.50
5: Wind sensor offset on NMEA1 IN: 0.00
6: Wind sensor offset on NMEA2 IN: 0.00
Q: return
Configure Baud rate (save & reboot after change)
0: NMEA INPUT (baud): 4800
1: NMEA OUTPUT (baud): 4800
2: RS-232 OUTPUT (baud): 115200
Q: return
Connect 0 mA reference, then press ENTER
Connect 24 mA reference, then press ENTER
OR
Connect 0 Volt reference, then press ENTER
Connect 5 Volt reference, then press ENTER

OMC-183-ML Manual Page 17
Command E: With ‘E’ the calibration values stored in the device can be requested
Current Input 2 (pin 60):
0 mA value: 407
24 mA value: 63055
Current Input 3(pin 63):
0 mA value: 421
24 mA value: 63132
Voltage Input 3(pin 66):
0 Volt value: 536
5 Volt value: 64310
Voltage Input 4(pin 69):
0 Volt value: 536
5 Volt value: 64309
Always use the ‘Q’ command “Save and exit menu” if you change anything.
Without your changes might be lost once the power is switched off!
After changing ‘baud rate’ reboot device as well.

OMC-183-ML Manual Page 18
5. EU DECLARATION OF CONFORMITY