DeltaOHM HD2016 Weighing Rain Gauge Instruction Manual

Operating manual
Weighing rain gauge
HD2016

INTRODUCTION

HD2016 is a rain gauge that detects the weight of the rainfall collected by a 400 cm 2 inlet. The sensor is a load cell located at the base of the rainfall collecting reservoir. The signal of the load cell is processed by the internal electronic board of the rain gauge in order to output the information on the rainfall. Many acquisition systems can be connected to the rain gauge, thanks to the multiplicity of outputs available:

• RS485 with Modbus-RTU or proprietary ASCII protocol
• SDI-12
• Voltage-free pulse contact output

Delta OHM offers a wide range of acquisition systems /data loggers for gathering the data detected by the rain gauge. The rain gauge is able to provide the total rainfall, the partial rainfall (from the last reset command or from the last reading command), and the average rainfall rate in the last minute and in the last hour.
The measured rainfall is regularly saved into a non-volatile memory, which retains the information even in case of power failure.
The automatic discharge of the rainfall collected allows using a compact and lightweight structure for the installation of the rain gauge. So as to ensure accurate measurement even with low-temperature climatic conditions, a version with heating that is automatically activated below +4 °C has been developed (HD2016R ) so that snow deposits and ice formations are prevented. If the discharge of the water collected takes place during a rainfall, a retention valve, located at the top of the rain gauge, temporarily holds the current rainfall, so as to avoid losing the amount of rainfall that falls while discharging.
The rain gauge is equipped with sophisticated features that allow reducing the effects of wind, ensuring better accuracy and stability of the measurement.
An NTC temperature sensor allows keeping under control the internal temperature of the instrument. The corrosion-resistant materials used and the absence of moving parts guarantee reduced maintenance and long operating life.
The rainfall collecting parts are treated with a nonadherent product for a better water flow. The rain gauge is factory calibrated and ready for use. A self-diagnostic system periodically checks the correct operation of the instrument and reports any anomalies. The rain gauge requires a 10…15 Vdc power supply.
When submitting your order , a bird dissuader, made of eight 3 mm diameter spikes, 60 mm in height, can be installed on the rain gauge upon request.

DESCRIPTION

1. Optional flange for the installation of the rain gauge raised above the ground.
2. Electronic board housing.
3. M12 connector for the connection of the measuring circuit power supply and signals.
4. Optional support rod for the installation of the rain gauge raised above the ground.
5. Optional flat base for fixing the support of the rain gauge raised above the ground.
6. Place the support rod.
7. Discharge of the rainfall collected.
8. Cover of the electronic board housing. To access the electronic board, loosen the 7 screws that secure the cover.
9. Terminal for protective earth connection.
10. Overflow drain.
11. Optional cable for the connection of the measuring circuit power supply and signals.
12. Cable gland for the heater power supply.
13. Port reserved for technical service.
14. Screws for fixing the cylindrical cover.
15. Cylindrical cover.

INSTALLATION

The instrument must be installed in an open area (any close objects should be at a distance equal to at least 4 times their height), away from buildings, busy roads, trees, etc., ensuring the space over it is free from all objects which could obstruct rain measurements, and in an easily accessible position for the filter to be cleaned periodically.
Although the rain gauge is equipped with features that allow reducing the effects of wind, for the best measurement accuracy it is recommended to avoid installation in areas exposed to turbulence (for example, do not install the instrument on the top of a hill, but on the side).
The rain gauge can be installed on the ground or raised 500 mm above the ground. Other sizes above the ground are available on request. For ground installation, three adjustable support feet, so that the instrument can be leveled correctly, and holes for fixing to the floor have been provided.
For raised installations, a flange to be fastened to the base of the instrument, and on which the support rod must be inserted, is provided. The rod may end with a flange so that it can be fixed to the floor.
For the measurement to be correct, it is important that the rain gauge is placed perfectly leveled; the base of the rain gauge is fitted with a bubble level.

3.1 ELECTRICAL CONNECTIONS
The measuring circuit power supply and the outputs (RS485, SDI-12, or contact) are connected via the male 8-pole M12 connector of the instrument (point 3 on page 4). Use a cable with a female 8-pole M12 connector and 0.7 mm2 (AWG 19) minimum wires section. Use a shielded cable over long distances. Upon request, CP18… cables with 5 or 10 m standard lengths are available (other lengths available upon request). The connections of the M12 connector and CP18… cable are listed below.

12/Black + 7/Violet
+ 6/Pink (‘)
2| Measuring circuit power supply positive (+Vdc)| 1/Red + 2/Blue +
4/Grey-Pink (*)
3| Not used| 3/Yellow
4| DATA – (RS485)| 9/White
5| DATA + (RS485) or SDI-12 line (depending on the setting of the switch SW1)| 5/Red-Blue
6| 1st pole of the voltage-free contact| 8/Grey
7| Not used| 10/Brown
8| 2nd pole of the voltage-free contact| 11/Green

(*) Wires shorted on the connector pin.
Fig. 3.1.1: M12 connector and CP18… cable

Connect the Protective Earth via the terminal under the base of the rain gauge (point 9 on page 4).
The heater power supply (only HD2016R) is connected directly to the internal terminal block.
Unscrew the cover of the electronic board (point 8 on page 4) and pass the cable through the cable gland (point 12 on page 4). Use a cable with 2.5 mm² (AWG 13) minimum wires section.
The heater power supply is isolated from the measuring circuit.
The following figure shows the electronic board.

=

WARNING FOR VERSION HD2016R:
In order to prevent possible burns by coming into contact with the heater, make sure that the heater is NOT powered when the cylindrical cover of the rain gauge is removed for cleaning or maintenance operations.

3.2 CHOOSING THE DIGITAL OUTPUT AND THE PROTOCOL
The selection of the type of digital output is done by means of the switch SW1 on the electronic board. Set the switch toward the RS485 or SDI-12 indication depending on the desired output.
The switch is set at the factory toward the RS485 indication (unless otherwise requested).
The switch S1 of the DIP switch on the electronic board allows selecting the communication protocol of the digital output at the instrument power-on. Set the switch S1 toward the MODBUS indication to select the standard protocol (Modbus-RTU or  SDI-12depending  on the digital output selected with the switch SW1), or set the switch toward the ASCII indication to select the ASCII proprietary protocol. If the standard protocol is selected, it is possible to switch to the ASCII proprietary protocol while the instrument is operating as described in the paragraph “ ASCII proprietary protocol ”. By default, the standard protocol is selected (Modbus-RTU or SDI-12 depending on the digital output selected with the switch SW1).
The setting of the switch SW1 and the DIP switch are read-only at instrument power-on, therefore they must be set before powering the instrument. The change of the setting of the switch SW1 and the DIP switch while the instrument is powered has no effect until the instrument is turned off and back on.
Note: the switch S2 of the DIP switch does not perform any function.
To change the other instrument settings, see the paragraph “ ASCII proprietary protocol ”.

3.3 RS485 CONNECTION
In the RS485 connection, the instruments are connected through a twisted-pair shielded cable for signals and the third wire for the ground.
Line terminations should be placed at the two ends of the network. The rain gauge has a built-in termination resistor, but it is not connected by default; if the rain gauge is at one end of the network, you can connect the built-in termination resistor by using the command COt of the ASCII proprietary protocol.
The RS485 output of the rain gauge is not isolated from the power supply.

The maximum number of devices that can be connected to the RS485 line (Bus) depends on the load characteristics of the devices to be connected. The RS485 standard requires that the total load does not exceed 32 unit loads; if the load is greater, divide the network into segments and add a signal repeater between a segment and the successive one. Line termination should be applied at both ends of each segment. The maximum length of the cable depends on the transmission speed and the cable characteristics. Typically, the maximum length is 1200 m. The data line should be kept separate from any power lines in order to prevent interference with the transmitted signal. Each instrument on the network is univocally identified by an address. Multiple transmitters with the same address should not be placed in the network. Before connecting the instrument to the network, set the address and, if necessary, the communication parameters.

3.4 SDI-12 CONNECTION
More SDI-12 sensors can be connected in parallel. The distance between a sensor and the acquisition system should not exceed 60 m.
Before connecting the instrument to an  SDI-12 network containing other sensors, set the address by using the proper SDI-12 command.

3.5 CONTACT OUTPUT

The voltage-free contact output simulates the pulse output of a tipping bucket rain gauge. The contact is isolated and is normally open. At 1-minute intervals, the output generates a pulse train (TON ≈ 60 ms, TOFF ≈ 60 ms) as a function of the rainfall measured in the previous minute. Each pulse corresponds to an amount of rainfall configurable from 0.001 to 1 mm/pulse (default=0.2) by using the command CP0 of the ASCII proprietary protocol.

3.6 UNLOCKING THE LOAD CELL

The load is locked for the transport of the rain gauge. Loosen the three nuts (point 14 on page 4) at the base of the cylindrical cover (point 15 on page 4) and remove the cylindrical cover by pulling it upwards. Unlock the load cell located at the base of the rain gauge by loosening the two screws on the sides of the cell and translating the locking support outward (fig.3.6.1). Replace the cylindrical cover and tighten the 3 fixing nuts.

3.7 FIXING THE RAIN GAUGE
For the measurement to be correct, it is important that the rain gauge is placed perfectly leveled; the base of the rain gauge is fitted with a bubble level.

For ground installation, secure the three support feet to the base of the instrument. Adjust the height of the feet so that the instrument is perfectly leveled. The instrument can be fixed to the floor by using the holes provided in the feet, close to the adjustment screws.

For raised installation, screw the support rod to the flange placed on the base of the instrument; the rod may end with a flange (HD2003.78) to be fixed to the floor.

ASCII PROPRIETARY PROTOCOL

The ASCII proprietary protocol is mainly used to set the operating parameters of the instrument by sending serial commands from a PC. The protocol can be used both with RS485 and SDI-12 physical interface. The rain gauge should be connected to the PC by using a converter from RS485 or SDI-12 (depending on the rain gauge output used) to USB or RS232C (depending on the PC port used). The use of the RS48 cable incorporating an RS485/USB converter is recommended. If a USB converter is used, it is necessary to install the relevant USB drivers on the PC.

NOTES ON THE INSTALLATION OF UNSIGNED USB DRIVER: before installing an unsigned USB driver into operating systems starting from Windows 7, it is necessary to restart the PC by disabling the driver signing request. If the operating system is 64-bit, even after installation the request of driver signing has to be disabled each time the PC is restarted.
The ASCII proprietary protocol can be activated both at instrument power-on and while the instrument is operating with the Modbus-RTU or SDI-12 protocols. In order to activate the ASCII proprietary protocol at the rain gauge power- on, the DIP switch S1 on the electronic board must be set to OFF (toward the ASCII indication, see figure 3.1.2 on page 7) before turning the instrument on. If activated at power-on, the protocol operates with the following communication parameters:

• Baud Rate = 57600
•  Data bits = 8
•  Parity = None (N)
•  Stop bits = 1
• Flow control = None

If the rain gauge is powered with the DIP switch S1 set to ON (toward the MODBUS indication on the electronic board), the Modbus-RTU or SDI-12 protocol, depending on the physical interface used, is activated by default. In this case, the ASCII proprietary protocol can be activated without turning the rain gauge off and without changing the setting of the DIP switch S1 by the following procedure:

1.  In the PC, start a serial communication program (many free programs suitable for the purpose can be found on the Internet), then set the COM port number to which the instrument is connecting and the communication parameters with which the instrument is operating (19200 8E1 by default for RS485 Modbus-RTU, 1200 7E1 for SDI-12).
2. Send the command ||| (sequence of three 124 decimal code ASCII characters followed by the Enter key). The instrument replies with @.
3. Within 10 seconds from the reply of the instrument, send the command @ (64 decimal code ASCII character followed by the Enter key). The instrument replies with address: &, where nnn is the address of the instrument (if the instrument does not receive the command @ within 10 seconds, the ASCII proprietary protocol is not activated; in this case, repeat from point 2). The ASCII proprietary protocol is now active keeping the communication parameters of the previous protocol (therefore, it is not necessary to change the settings of the serial communication program). To disable the ASCII proprietary protocol after use and return to the previous protocol, send the command # (or power cycle the instrument).

After activation of the ASCII proprietary protocol, the serial commands given below can be sent. To change the rain gauge parameters, the serial command CAL USER ON must be sent first (the instrument replies with the address: USER ENABLED!). In order to cancel the command CAL USER ON, send the command CAL END (the instrument replies with address: LOCKED). The command CAL USER ON is automatically disabled after 5 minutes of inactivity. If the settings should be only read, the command CAL USER ON is not required.

Instrument general information

Reservoir discharge

valve:
state= Opened ⇒ valve has been opened
state= Closed ⇒ valve has been closed
COa| address: &| Activates the discharge after 20 minutes from the end of the rainfall if the reservoir filling percentage is greater than or equal to 80% (2400 cc)
COb| address: &| Activates the discharge after 20 minutes from the end of the rainfall if the reservoir filling percentage is greater than or equal to 10% (300 cc)
RDE| address: delay| Reads the delay time before running the discharge at the end of a rainfall (default = 20 minutes)
CDE nnn| address: &| Activates the discharge after nnn minutes (20 ≤ nnn ≤480) from the end of the rainfall if the reservoir filling percentage is greater than the set threshold
RTE| address: percentage| Reads the reservoir filling percentage that enables the discharge (default = 10% ⇒ 300 cc)
CTE nn| address: &| Activates the discharge (after the delay time set) if the reservoir filling percentage is greater than nn % (1 ≤ nn ≤ 99)

Note: the discharge takes place normally at the end of rainfall after the delay time set; if the reservoir should overfill during rainfall, the discharge will take place during the rainfall and the upper retention valve will close to maintain the current rainfall in the upper part of the rain gauge; at the end of the discharge phase, the rainfall collected in the upper part of the rain gauge will be discharged in the main reservoir and weighted.

Upper retention valve

valve:
state= 0 ⇒ valve is not enabled
state= 1 ⇒ valve is enabled
COv n| address: &| Enables/disables the use of the upper retention valve:
n= 0 ⇒  disable ; n= 1 ⇒  enable
CVH| address: state&| Change the state of the upper retention valve:
state= Opened ⇒ valve has been opened
state= Closed ⇒ valve has been closed

Heater
The HD2016R rain gauge has a temperature sensor that detects the internal temperature of the instrument ( not the air temperature ). The heater is activated when the internal temperature falls below the value set with the command CTL (default 4 °C) and is switched off when the internal temperature rises above the value set with the command CTH (default 10 °C).

(default = 10.0 °C)
CTH nn.d| address: &| Sets the heater deactivation temperature to the value nn.d, (activation temperature ≤ nn.d ≤ 10.0 °C)
RTL| address: temperature| Reads the heater activation temperature (default = 4.0 °C)
CTL nn.d| address: &| Sets the heater activation temperature to the value nn.d (4.0 °C ≤ nn.d ≤ deactivation temperature)
RTD| address: state| Reads the heater enabling state:
state= Enabled ⇒ heater is used
state= Disabled ⇒ heater is not used
CTD n| address: &| Enables/disables the use of the heater:
n= 0 ⇒  disable ; n= 1 ⇒  enable
CHS| address: state&| Changes the activation state of the heater:
state= On ⇒ heater has been switched on
state= Off ⇒ heater has been switched off

Resolution of contact output

contact output (default = 0.200 mm/pulse)
CP0 n.ddd| address: &| Sets the resolution of the contact output to the value
n.ddd mm/pulse (max. 1 mm/pulse)

Counters reset

It must be run before the total weight counter reaches the maximum value of 999,999,999 mg

RS485 settings

resistor of the RS485 output:
state= 0 ⇒ termination resistor not connected
state= 1 ⇒ termination resistor connected
COt n| address: &| Connect/disconnect the termination resistor of the RS485 output: n= 0 ⇒ disconnect ; n= 1 ⇒Þ connect
RMA| address: address address| Reads the Modbus address (default = 1)
CMA nnn| address: &| Sets the Modbus address to nnn (1…247)
RMB| address: baud rate index MB baud| Reads the Modbus Baud Rate:
Baud rate index= 0 ⇒  1200 Baud rate index= 1 ⇒  2400 Baud rate index= 2 ⇒  4800 Baud rate index= 3 ⇒  9600
Baud rate index= 4 ⇒  19200 (default)
CMB n| address: &| Sets the Modbus Baud Rate of index n:
n= 0 ⇒  1200 ;  n= 1 ⇒  2400 ;  n= 2 Þ 4800
n= 3 ⇒  9600 ;  n= 4 ⇒  19200
RMP| address: mode index MB mode| Reads the Modbus transmission mode:
mode index= 0 ⇒  8N1
mode index= 1 ⇒  8N2
mode index= 2 ⇒  8E1 (default)
mode index= 3 ⇒  8E2 mode index= 4 Þ 8O1 mode index= 5 Þ 8O2
(N=no parity, E=even parity, O=odd parity)
CMP n| address: &| Sets the Modbus transmission mode:
n= 0 ⇒  8N1 ; n= 1 Þ 8N2  ; n= 2 ⇒  8E1
n= 3 ⇒  8E2  ; n= 4 ⇒  8O1 ; n= 5 ⇒  8O2
(N=no parity, E=even parity, O=odd parity)
RMW| address: delay index MB Tx delay| Reads the receiving mode after the Modbus transmission:
delay index= 0 ⇒  Violate protocol and go in receiving mode right after Tx
delay index= 1 ⇒ Respect protocol and wait for 3.5 characters after Tx (default)
CMW n| address: &| Sets the receiving mode after the Modbus transmission:
n= 0 ⇒  Violate protocol and go in receiving mode right after Tx
n= 1 ⇒  Respect protocol and wait for 3.5 characters after Tx

Printing the measures

n=0 ⇒ Status register content in hexadecimal
n=2 ⇒ Partial rainfall, in µm, from the last reading command
n=4 ⇒ Total rainfall in µm
n=6 ⇒ Partial rainfall, in µm, from the last reset command
n=8 ⇒ Average rainfall rate, in µm/min, calculated in the last minute
n=10 ⇒ Average rainfall rate, in µm/h, calculated in the last hour
n=12 ⇒ Rain gauge the internal temperature in °C
n=14 ⇒ Rainfall total weight (Pmg) in mg ()
n=16 ⇒ Rainfall total weight, in mg, considering the evaporation (WMG) ()
n=18 ⇒ Weight, in mg, of the current reservoir content (Tmg) ()
n=20 ⇒ Partial rainfall, in mils, from the last reading command
n=22 ⇒ Total rainfall in mils
n=24 ⇒ Partial rainfall, in mils, from the last reset command
n=26 ⇒ Average rainfall rate, in mils/min, calculated in the last minute
n=28 ⇒ Average rainfall rate, in mils/h, calculated in the last hour
n=30 ⇒ Rain gauge the internal temperature in °F
() For details on weight measurements, please see the paragraph “Notes on weight measurements”.
RR n| address: measured value| Continuous print (once per second) of the measure of index n (see the command SR for the indexes)
S0| String with 16 fields| Single print of all the measures:
campo 1 ⇒ & followed by a control code
campo 2 ⇒ Filling percentage of the rain gauge reservoir
campo 3 ⇒ Weight, in mg, of the current reservoir content (Tmg) ()
campo 4 ⇒ Rainfall total weight, in mg, considering the evaporation (WMG) ()
campo 5 ⇒ Rainfall total weight (Pmg) in mg ()
campo 6 ⇒ Partial rainfall, in µm, from the last reset command
campo 7 ⇒ Average rainfall rate, in µm/min, calculated in the last minute
campo 8 ⇒ Average rainfall rate, in µm/h, calculated in the last hour
campo 9 ⇒ Reservoir status (Evap if in evaporation, Rain if in precipitation) followed by (valid data) or! (invalid data)
campo 10 ⇒ Indicates how long the status reported in the previous field has been active camp 11…15 ⇒ Confidential information campo 16 Þ Internal temperature in °C
(*) For details on weight measurements, please see the paragraph “Notes on weight measurements”.
R0| String with 16 fields| Continuous print (once per second) of all the measures (see the command S0 for the fields)
ST| address: & voltage status_register| Prints the supply voltage in Volt and the content of the status register in hexadecimal
SS| address: status_register| Prints the content of the status register in hexadecimal- mal
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MODBUS-RTU PROTOCOL

For enabling the Modbus-RTU protocol, set on the electronic board, before powering the instrument, the DIP switches S1 to ON, toward the MODBUS indication, and the switch SW1 toward the RS485 indication (see figure 3.1.2 on page 7). In Modbus-RTU mode, the instrument sends the detected measurements only if specifically requested by the PC, PLC or data logger.

The default communication parameters are

• Baud Rate = 19200
• Data bits = 8
• Parity = Even (E)
• Stop bits = 1
• Flow control = None

The communication parameters can be changed by using the appropriate serial commands of the ASCII proprietary protocol or, alternatively, directly with Modbus commands by changing the value of the Holding Registers described later.
The function code 04h (Read Input Registers) allows reading the values measured by the instrument. The following table lists the Input Registers available.

Modbus Input Registers

integer
10,11| Average rainfall rate, in µm/h, calculated in the last hour| 16-bit integer
12,13| Rain gauge the internal temperature in °C| 16-bit integer
14,15| Rainfall total weight (Pmg) in mg ()| 16-bit integer
16,17| Rainfall total weight, in mg, considering the evaporation (Wmg) ()| 16-bit integer
18,19| Weight, in mg, of the current reservoir content (Tmg) (*)| 16-bit integer
20,21| Partial rainfall, in mils, from the last reading command| 16-bit integer
22,23| Total rainfall in mils| 16-bit integer
24,25| Partial rainfall, in mils, from the last reset command| 16-bit integer
26,27| Average rainfall rate, in mils/min, calculated at the last minute| 16-bit integer
28,29| Average rainfall rate, in mils/h, calculated in the last hour| 16-bit integer
30,31| Rain gauge the internal temperature in °F| 16-bit integer

(*) For details on weight measurements, please see the paragraph “Notes on weight measurements”. The measures are signed 32-bit integer values. Two consecutive 16-bit registers must be accessed to read a measure.
The register with a lower address (for example the register with address 12 for the temperature in °C) contains the most significant bits.
Some operating parameters of the instrument can be changed directly with Modbus commands by setting the value of the Holding Registers with the function code 06h (Write Single Register) or 10h (Write Multiple Registers). The following table lists the Holding Registers available.

Modbus Holding Registers

the command has been executed correctly.
If 1 , command execution errors occurred.| 16-bit integer
1| Indicator of the correct permanent storage of the parameters. If 0 , the parameters have been stored correctly.
If 1 , storage errors occurred.| 16-bit integer
2| Content of the status register| 16-bit integer
8| Heater enabling/disabling.
Write A500 h to enable the use of the heater. Write A501 h to disable the use of the heater.| 16-bit integer
9| Reset all the counters.
Write A55A h to reset the counters.| 16-bit integer
10| Reset the partial rainfall value. Write A55B h to reset the value.| 16-bit integer
11| Reservoir discharge cycle.
Write A55A h to run the discharge cycle.| 16-bit integer
100| Modbus address (from 1 to 247, default=1).| 16-bit integer
101| Modbus Baud Rate.
If 0 , the Baud Rate is 9600. If 1 , the Baud Rate is 19200 (default).| 16-bit integer
102| Modbus transmission mode.
0 Þ 8N1, 1 ⇒  8N2, 2 ⇒  8E1 (default), 3 ⇒  8E2, 4 Þ 8O1, n= 5 ⇒  8O2 (N=no parity, E=even parity, O=odd parity)| 16-bit integer
103| Receiving mode after the Modbus transmission (Tx).
0   ⇒  Violates the protocol and goes immediately in reception mode after Tx
1   ⇒  Respects the protocol and waits for 3.5 characters after Tx (default)| 16-bit integer

In order to check whether the last writing operation has been completed successfully, verify that the Holding Register with address 0 contains 0 by using the function 03h (Read Holding Registers).
The 06h and 10h writing functions change only the value of the parameters in the RAM memory, the change is therefore canceled in case of a power supply failure in the instrument.
For making the change permanent, write the hexadecimal value FF00 in the Coil with address 2 by using the 05h function code (Write Single Coil). The command 05h must be sent within 10 seconds from the last 06h or 10h command.

Modbus Coils

In order to check whether the permanent storage has been completed successfully, verify that the Holding Register with address 1 contains 0, by using the function 03h (Read Holding Registers).

SDI-12 PROTOCOL

For enabling the SDI-12 protocol, before powering the instrument set on the electronic board the DIP switch S1 to ON, toward the MODBUS indication, and the switch SW1 toward the SDI-12 indication (see figure 3.1.2 on page 7).

The instrument is in compliance with version 1.3 of the protocol. The communication parameters of the protocol are:

• Baud Rate = 1200
• Data bits = 7
• Parity = Even (E)
• Stop bits = 1

Communication with the instrument is performed by sending a command in the following format:
< Address>!
With