BASIC

EVO

Module and Communication
Description for Firmware Version
5.51

Page 1

Contents
1

General ............................................................................................................................................ 4
1.1

For your safety......................................................................................................................... 4

1.2

Intended use ............................................................................................................................ 4

1.3

Implementation guidelines ..................................................................................................... 5

1.4

Loss of warranty / liability / disclaimer ................................................................................... 5

2

Mounting / installation site ............................................................................................................. 63

Configuration and characteristics of the terminal pins on the BASICEVO ......................................... 7
3.1

Current consumption .............................................................................................................. 74

LED status display ............................................................................................................................ 8

5

Data interfaces ................................................................................................................................ 8

6

5.1

Function of the COM signal (communication) ........................................................................ 8

5.2

Data exchange between the master and BASICEVO (slave) ...................................................... 8

Modbus communication ................................................................................................................. 9
6.1

Automatic detection of baud rate, framing format and Modbus dialect ............................. 10

6.2

Structure of Modbus data telegrams .................................................................................... 10

6.3

Modbus communication device ............................................................................................ 11

6.4

Modbus slave ID .................................................................................................................... 11

6.5

Modbus control commands .................................................................................................. 13

6.5.1

Control command 0x03 → Read Holding Register ........................................................ 13

6.5.2

Control command 0x06 → Write Single Register.......................................................... 14

6.6
7

8

9

Calculating the checksum ...................................................................................................... 16

Register overview .......................................................................................................................... 17
7.1

Meaning of the individual bits in the status bit bar (SYS_Status): ........................................ 18

7.2

Description of the unit code: ................................................................................................. 19

Information on start-up and operation ......................................................................................... 19
8.1

Self-test + warmup ................................................................................................................ 19

8.2

Setting the zero point ............................................................................................................ 20

8.3

Setting the end point ............................................................................................................. 20

8.4

Calculating the correction value for the end point ............................................................... 20

8.5

Restoring the calibration parameters to factory settings ..................................................... 20

Annex ............................................................................................................................................. 21
9.1

Mechanical dimensions [mm] ............................................................................................... 21

9.2

Operation of the BASICEVO on a microcontroller ................................................................... 22
Page 2

9.3

Operation of the BASICEVO on a PC ........................................................................................ 23

9.4

Installation of the BASICEVO in a Modulbox with gas adapter................................................ 23

10

Legal information ...................................................................................................................... 24

Page 3

1

GeneralThe BASICEVO is a further development the tried-and-tested smartMODULBASIC, which has been
improved in many ways. Its convenient interfaces make it quick and easy to integrate into existingmeasuring and control systems.
The most important changes in the smartMODULBASIC compared to the the BASICEVO:
•
•
•
•
•

Expanded operating voltage range of 3.3 V – 6.0 V DC (+/-5%)
Status display via 2 LEDs (red/green)
Upgraded software, powerful processor
Improved mechanical setup, more aesthetic design
Modbus ASCII (standard and smartGAS-specific) and RTU protocols supported

The BASICEVO is based on the physical measurement method of infrared absorption, and in addition toits selectivity, it provides the best conditions for reliable and precise measurements.
Its compact design and the low maintenance effort make it ideal for use in difficult conditions.
1.1 For your safety
Meaning of warning signs
The following warning signs are used in this document to indicate the corresponding warning texts.
CAUTION!

Indicates a potential hazardous situation. If this is not avoided, injuries or damage to the product orenvironment may occur.
Also warns against improper use.
NOTE

Information on the use of the product
Before connecting and using the BASICEVO, ensure that you have fully read and understood these
instructions. Please contact our Service department if you have any questions or if anything is unclear.
Warning signs indicate important information.
Keep these instructions in a safe place or give them to the device operator for safe keeping if necessary;
if the device is sold, the instructions must be transferred to the purchaser. When installing andoperating the device, you must follow the statutory requirements and guidelines that relate to thisproduct!
1.2 Intended use
The BASICEVO is a gas measurement cell with independent measurement capabilities and is used todetermine gas concentrations in accordance with its specifications. It is not suitable for any othermeasurement or testing purposes and must not be used in any other way.

Page 4

CAUTION!

The sensor must not be operated in potentially explosive environments or under harsh conditions(e.g. high, condensing humidity, heavy air flow, in aggressive atmospheres or outdoors without ahousing).
1.3

1.4

Implementation guidelines•

We recommend installing the BASICEVO in a closed gas space, e.g. using a Modulbox (seechapter 9.4).

•

Frequent ZERO point check and adjustment – requires appropriate zero gas•

Frequent SPAN adjustment – requires appropriate test gas•

Before applying any form of adjustment, leave the sensor in operation for at least 30 minutes
under stable environmental conditions•

Data communication via UART (B3 series) or RS485 (with connect interface) with Modbus
RTU
Loss of warranty / liability / disclaimer
CAUTION!

Opening the sensor as well as manipulating or damaging the device will invalidate the warranty!
The warranty may also be invalidated if aggressive chemicals are used, contamination occurs,
liquids penetrate the device or the instructions in this module and communication description are
not observed!
smartGAS Mikrosensorik GmbH assumes no liability for consequential loss, property damage or
personal injury caused by failing to observe the the module and communication description.

Page 5

2

Mounting / installation site

The BASICEVO has two fastening lugs (Figure 1) on the sides. These fastening lugs enable the device tobe screwed in place by M3 bolts. Use only bolts with a flat seating surface, e.g. cylinder head bolts acc.
to DIN 84, fillister head screws acc. to DIN 7985 or similar, but never countersunk bolts
The smartGAS sensors allow for installation in various positions on the customer's devices. Since thecalibration ex factory cannot cover every installation situation and ambient condition, the zero andend point need to be checked after installation and recalibrated if necessary. In any case werecommend a functional test of every device after final installation in the customer's application aspart of commissioning.

Figure 1: Fastening lugs -  3.2 mm

CAUTION!

Infrared gas sensors are optical measuring systems. Severe impacts and vibrations must therefore
be avoided!

NOTE

It is essential to ensure that the sensor is not exposed to the following influences at the installation
location: high humidity (condensing), extreme temperature fluctuations, mechanical loads (e.g.
vibrations), dust, dirt. No aggressive cleaning agents or adhesives may be used. The BASICEVO mustnot be modified in any way whatsoever. Under no circumstances may liquid or dirt be allowed topenetrate the inside of the device!

Page 6

3

Configuration and characteristics of the terminal pins on the BASICEVOThe BASICEVO is connected to the power supply via a 4-pin connector strip
with a grid dimension of 2 mm. The required socket is not supplied as standard with the BASICEVO. It
can, however, be ordered as a separate item.

Figure 2: Pin assignment of the connector strip on the BASICEVO

Connector ST1
Pin Assignment
1 +Vcc 3.3 – 6.0 V DC (+/-5%)
2 GND
3 COM
4 NC (Do not connect)
Table 1: ST1 pin assignment

3.1 Current consumption
The following table shows an overview of the current and power consumption. It is strongly
recommended to only use adequately dimensioned and voltage-stabilized supply voltages in order toprevent malfunctions due to voltage dips.
Appropriate cable diameters must be used for long supply lines in order to avoid excessive
voltage drops over the lines!
Supply voltage
3.3 V
6.0 V

Current
consumption
500 mA
240 mA

Table 2: Voltage-dependent power consumption

NOTE

The power consumption can be briefly higher when the BASICEVO is switched on.

Page 7

4

LED status display

Two LEDs (green/red) are located next to the connector strip. These show the current device status as
per Table 3:
LED1

LED2

Figure 3: Position of the status LEDs

LD1 (green) O LD2 (red) O
flashes
illuminates
flashes
illuminates

Device status
Start phase / self-test (approx. 40 seconds)
Normal operation
Measurement overrange or underrange (OUT_OF_RANGE)
Device error / contact service
Table 3: LED status display

NOTE

Measurement overrange or underrange (OUT_OF_RANGE) can be switched on or off.

5

Data interfaces

5.1 Function of the COM signal (communication)
The BASICEVO has a semi-duplex UART data interface that supplies and evaluates the non-inverted UART
signals. The semi-duplex operation also means that only one communication signal (COM) is required.
The level on the COM line is between 0 V and +3.3 V. It may therefore be necessary to include a leveladjustment system depending on the communication partner (master) that is connected.

CAUTION!

The COM connection is designed as an open-collector connection with an internal pull-up resistorof 10 kOhm at 3.3 V. It is wired to GND and may be loaded with a maximum of 30 mA. Under nocircumstances may the voltage exceed 7 V DC. The use of protective resistors, EMC filters, electricalisolation and other electrical or electronic measures may cause communication problems and must
therefore be carefully considered by specialist personnel.
5.2 Data exchange between the master and BASICEVO (slave)
Figure 4 shows a possible scenario between the master and BASICEVO (= slave).
The following times refer to Modbus ASCII and a baud rate of 2400 Bd.

Page 8Figure 4: Time diagram – Data exchange between master and BASICEVO (slave)

The duration of a query string is 70 – 73 ms. A short pause may follow afterwards (max. 400 ms). The
module response then occurs. This depends on the number of bytes that are read out. If only one byte
is read out, the module response is around 70 ms. When multiple bytes are read out, the response
phase is extended accordingly.
Generally speaking, the BASICEVO sensor responds to a query within 400 ms. The character string is thensent immediately without a response pause.

CAUTION!

At higher baud rates (> 2400 Bd), significantly faster response times can be expected.

NOTE

The cable used for wiring should be twisted and shielded (twisted pair cable).

6

Modbus communication

The BASICEVO supports the Modbus protocol in ASCII and RTU mode thanks to its serial semi-duplex
interface. In ASCII mode, in addition to the standard variant, there is a smartGAS-specific derivativethat has a different checksum calculation.
In principle, Modbus communication functions on the basis of a query/response mechanism. The
master sends the query to one of possibly several slaves (subscribers). Each connected subscriber
therefore receives a subscriber address that is unique in the network. Only the subscriber that has
found its address in the query from the master will respond.
The type of query is determined by a control command (function code). This can be about writing dataor reading data to/from the subscriber, for example. Depending on the control command, there is adata portion for both the query and the response.

Page 9Each query and each response must be clearly identified by its beginning and by its end. The use of acheck field (=check word / CRC) is provided for in the protocol to enable any possible communication
errors to be detected. The Modbus derivatives implement this in different ways.
You can obtain detailed information about the Modbus protocol at www.modbus.org
6.1 Automatic detection of baud rate, framing format and Modbus dialect
The BASICEVO firmware is provided with automatic configuration detection. This means that the sensor
automatically detects the baud rate, the framing as well as the Modbus dialect used after it is switchedon and interacts on the bus line for the first time in the system.
The framing formats and Modbus baud rates listed in Table 4 harmonise with each another and can be
freely combined among each other.
Framing formats and Modbus baud rates
Data bits
ParityStop bit
Baud rates 
7E
1
2400Bd7E24800Bd7O
19600Bd7
O
2
9200Bd7N238400Bd
8E
157600Bd
8N
1115200Bd
8
N
2
8
O
1
Table 4: Freely combinable framing formats / baud rates

NOTE

A framing format of 8 data bits must be used for the communication via Modbus RTU.
6.2 Structure of Modbus data telegrams
As previously mentioned elsewhere, smartGAS Mikrosensorik recommends creating a data telegramwith Modbus RTU. It is also possible to create the data telegram with Modbus ASCII, but this is not
explained here. The following tables show the basic structure of an RTU data telegram:
Dialect
Modbus
RTU

Start

Slave ID
1 bytee.g.:0xA0

Function
1 bytee.g.:0x03

Data
0 to 1x252 bytes
e.g.:0x00,0x05, 0x00,0x02

CRC
2 bytese.g.:0xA4, 0xD3

End

Communic
ation

Pause
3.5
character
s

0xA0

0x03

0x00,0x05,0x00,0x02

0xA4, 0xD3

Pause
3.5
characters

In RTU mode, each byte is transferred unchanged. This necessarily means that UART frames with 8
data bits need to be used in RTU mode. The advantage of RTU mode is the more effective utilisationof the interface: Only around half of the data volume needs to be transmitted compared to the ASCII
mode.

Page 10

6.3 Modbus communication device
Figure 5 shows the basic state diagram of the transmission and receiving devices, regardless ofwhether master or slave:
Receive ‘:’ (0x3A) / empty
receive buffer
Receive ’:’ (0x3A)

Wait(ready to send or
receive)

Receive

RequestReceive ‘LF’ (0x0A) / checkreceived telegram (LRC, parity,
slave address, etc.)

Receive characters / setcharacters in the receive
bufferStart
sending

Send’:’ (0x3A)

Receive CR(0x0D)
Send all characters

Send

Send ’CR’,‘LF‘(0x0D, 0x0A)

Sending end

Receive ’:’ (0x3A)/
Empty receive buffer

Wait for end oftelegram

Figure 5: State diagram of a Modbus subscriber (ASCII operating mode)

If an incomplete query is sent to the BASICEVO, it does not return a response. The module behaves thesame when at least one register in the register area being queried does not exist. Error-free telegrams
are processed. Faulty telegrams are not answered.
6.4 Modbus slave ID
With the BASICEVO sensor, the as-delivered device address (slave ID) corresponds to the last two
numbers of the serial number on the type plate.
In individual operation:
If only one device is connected with the Modbus master, the sensor module can be queried via the
global slave ID 248.
In multiple operation:
If several devices are connected to the Modbus master, the sensor modules must be queried via theirslave ID. The sensor modules cannot be queried via the global slave ID 248.

Page 11

NOTE

Example for calculating the Modbus address:
Device address = #35 decimal → 0x23 hex
If the serial number ends with “00”, the address is always #100 decimal =0x64 hexadecimal.
The address “0” must never be used!
Figure 6: is a flow diagram that shows how unknown Modbus module addresses can be determined.
Any register (e.g. serial number) can be queried via all module addresses (1 – 247) with a timeout of
one second. If a module is queried with the correct address, it reacts by sending a response. The
module address is included in this response. Thus, at the end of the search cycle, module responses
can be used to analyse which module addresses are presently connected to the bus system. When theserial numbers are queried, it is then possible to conclude which address is assigned to which module.
The permitted address range for BASICEVO is between 1 and 247. According to the Modbus
specification, the addresses 248 – 255 are reserved. Address 0 stands for broadcast and must not beused!
Connect module

START

Timeout := 1 s:

Query telegram for reading out the serial number
Addr.
03
0086
0004
LRC
CRLF

Addr.: = 1 to 247 STEP 1
Calculate LRC

Send query

Timeout?

Yesno
Valid response

Ye
s

no
no
Output serial no.
and addressYes

Figure 6:: Flow diagram – Determining module addresses

Page 12

6.5 Modbus control commands
Communication with the BASICEVO sensor is supported by only two function codes:• 0x03 – Read Holding Registers (multiple)• 0x06 – Write Single Register (single)
One register is 16 bits wide and thus consists of 2 bytes:
Register…

15
High Order Byte - Hi

0
Low Order Byte - Lo

All the BASICEVO data that the user can access is shown on registers that are 16 bits wide each.
6.5.1 Control command 0x03 → Read Holding Register
This control command allows you to read values from the BASICEVO sensor. Notethat only the registers defined in these instructions can be read. Therefore, thismust be checked especially when multiple registers are queried.
Query

Response

Meaning of the data(according to ASCII table)

Field
Modbus address

(hex)
0xXX

Field
Modbus address

(hex)
0xXX

Function

0x03

Function

0x03

Start Register Hi

0x00

Byte count

0x08

Start Register Lo

0x80

Register value Hi (128)

0x53

‘S’

Register count Hi

0x00

Register value Lo (128)

0x4D

‘M’

Register count Lo

0x04

Register value Hi (129)0x46‘ ’ = Empty characters

Checksum Lo

0xXX

Register value Lo (129)

0x43

‘C’

Checksum Hi

0xXX

Register value Hi (130)

0x4F

‘O’

Register value Lo (130)

0x32

’2’

Register value Hi (131)0x20‘ ’ = Empty characters

Register value Lo (131)0x20‘ ’ = Empty characters

Checksum Lo

0xXX

Checksum Hi

0xXX

Example 1: Reading out the 4 registers for “Device Type”

In this example, four registers of the BASICEVO sensor were queried starting from the register start
address 0x0080 (decimal 128). The response consisted of a payload of 8 bytes that can be resolved
with the aid of the ASCII table. Example: Response HEX 53 → to ASCII table → letter S
The response is now: “SM CO2”. Thus it is a BASICEVO sensor (SM)for the measuring gas carbon dioxide (CO2).

Page 13

QueryField
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x03
0x00
0x0A

Response
Field
Modbus address
Function
Byte countRegister value Hi (14)

(hex)
0xXX
0x03
0x02
0x01

Meaning of the data

Register count Hi

0x00

Register value Lo (14)0xC8Register count Lo

0x01

Checksum Lo

0xXX

Checksum Lo

0xXX

Checksum Hi

0xXX

Checksum Hi

0xXX

456

Example 2: Reading out the “Conc” register (for displaying the gas concentration)

In this example, one register was queried starting from the register start address 0x0A (decimal 10).
The two data bytes were transmitted combined as a hexadecimal value. If this value (01C8) isconverted to a decimal number, the result is a concentration value of 456.
Query
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x03
0x00
0x4F

Response
Field
Modbus address
Function
Byte countRegister value Hi (14)

(hex)
0xXX
0x03
0x02
0x00

Register count Hi

0x00

Register value Lo (14)0x03

Register count Lo

0x01

Checksum Lo

0xXX

Checksum Lo

0xXX

Checksum Hi

0xXX

Checksum Hi

Meaning of the data

3, means ppm x 1

0xXX

Example 3: Reading out the “Unit” registerIn this example, one register was queried starting from the register start address 0x004F (decimal 79).
The two data bytes were transmitted combined as a hexadecimal value. If this value (0x0003) isconverted to a decimal number, the result is “3”. This stands for the unit ppm with the scaling x 1.
Combined with the data from examples 1 and 2, the BASICEVO sensor that was read here has therefore
measured a gas concentration of 456 ppm CO2.

6.5.2 Control command 0x06 → Write Single Register
This command enables a new value to be systematically written to an addressed register. However, it
is only possible to write to those registers intended for this purpose.
Query
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x06
0x00
0xC0

Response
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x06
0x00
0xC0

Meaning of the data

Register count Hi

0x00

Register count Hi

0x00

Register count Lo

0xA0

Register count Lo

0xA0

Checksum Lo

0xXX

Checksum Lo

0xXX

Checksum Hi

0xXX

Checksum Hi

0xXX

The new address of themodule (160)

Example 4: Writing to the “Modbus_address” register

Page 14

In this example, a new Modbus address 0xA0 (hex) = 160 dec. was assigned to the BASICEVO sensor.
Once this communication sequence is complete, the device is only responsive at this new address!
NOTE

The address 0 as well as addresses > 247 must not be assigned!
Query
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x06
0x00
0x47

Response
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x06
0x00
0x47

Meaning of the data

Register count Hi

0x00

Register count Hi

0x00

Register count Lo

0x01

Register count Lo

0x01

Checksum Lo

0xXX

Checksum Lo

0xXX

Checksum Hi

0xXX

Checksum Hi

0xXX

The zero point has been
reset

Example 5: Writing to the IR_4tagneu register (setting the zero point)

In this example, the zero point of the BASICEVO sensor has been reset. This was done by writing thevalue 1 to register 0x0047 (decimal 71). The device subsequently internally calculated and saved thecurrent correction value for the zero point. The value of the correction is then shown when the sameregister is read out.
NOTE

The zero point must only be set when zero gas has been applied and the concentration value
subsequently remains stable.
Query
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x06
0x00
0x54

Response
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0xXX
0x06
0x00
0x54

Meaning of the data

Register count Hi

0x27

Register count Hi

0x27

Register count Lo

0x10

Register count Lo

0x10

Checksum Lo

0xXX

Checksum Lo

0xXX

Checksum Hi

0xXX

Checksum Hi

0xXX

Correction value has been
set to 10000

Example 6: Writing to the SPAN register (end point correction comparison)In this example, a new end point correction has been set for the BASICEVO sensor. A value of 2710 (hex)= 10000 (decimal). This is also the delivery condition. A value of 11000 would mean, for example, thatthe concentration value displayed is 10% higher than internally measured. This register therefore
makes it possible to correct deviations in the concentration display of the BASICEVO sensor.

NOTE

The end point must only be set in this way when a suitable test gas is applied and the concentration
value subsequently remains stable!
Before the end point is set, the zero point must have previously been set correctly.

Page 15

6.6 Calculating the checksum
The calculation of the checksum CRC specifically for the RTU operating mode will now be explained
based on an example. How the calculation of the LRC checksums in ASCII standard works is describedthoroughly in the documentation of the Modbus standard.
The checksum is calculated via the slave ID, the function and the associated data (start register andregister count). As an example, we generate a query for reading the Conc register from the BASICEVO
sensor with the address 14 (decimal) = 0E (hex.)
Query
Field
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0x0E
0x03
0x00
0x0A

Register count Hi

0x00

Register count Lo

0x01

Checksum Lo

0xXX

Checksum Hi

0xXX

Therefore, in hexadecimal format, the resulting byte string is 0x0E, 0x03, 0x00, 0x0A, 0x00, 0x01. The
checksum is now created; here is an example code for calculating the CRC checksum:
C# example to calculate modbus RTU checksum:/// <summary>/// Calculates the checksum of an modbus RTU message and adds it to the end(last 2 bytes).
/// </summary>/// <param name="Databytes"></param>/// <returns></returns>
private void Calculate_CRC(ref byte[] Databytes){
UInt16 v_CRC = 0xFFFF;
for (int x = 0; x < Databytes.Length - 2; x++){v_CRC ^= (UInt16)Databytes[x];// XOR byte into least sig.
byte of crc
for (int y = 8; y != 0; y--){// Loop over each bit
if ((v_CRC & 0x0001) != 0){// If the LSB is set
v_CRC >>= 1;
v_CRC ^= 0xA001;}
else
v_CRC >>= 1;}// Shift right and XOR 0xA001// Else LSB is not set// Just shift right}}

Figure 7: Code example for creating CRC checksums

After the calculation of the checksum and the end code, the following data string would then be sent:
0xF7A4

Page 16

QueryField
Modbus address
FunctionStart Register Hi
Start Register Lo

(hex)
0x0E
0x03
0x00
0x0A

Register count Hi

0x00

Register count Lo

0x01

Checksum Lo

0xA4

Checksum Hi

0xF7

The checksum is included each time data is sent and is then recalculated by the recipient. If the data
set is corrupted or adulterated, the checksum calculated at the recipient would deviate from the one
which was sent. The data set would then be unusable.

7

Register overview

All of the registers listed below are holding registers.
Address
Name
R/W
Data
Function / description
type
0x0003 T_m
R/--- signed
Measured value for internal temperature (x0.1°C)
number0x0009 Sys_status
R/--- number
Status bit bar, see page 18 for details
0x000A Konz
R/--- signed
Measured value for gas concentration in ppm,
numbervol.% or %LEL (Please note unit code!)
0x0047 IR_4tagneu
R/W number
Zero point reference value.
0x004F Einheit
R/--- number
Unit code and scaling factor for the concentration.
Details and calculation example later in thisdocument.
0x0051 Konz_fs
R/--- number
Upper range value (full scale) of theconcentration.
0x0054 SpanR/W number
End point reference value.
Value must be between 5000 and 15000;
otherwise it is reset to 10000.
0x0059 fab_zero_value R/--- signed
Correction factor for
numberzero point calibration ex works
0x005A fab_span_value R/--- signed
Correction factor for
numberspan calibration ex works
0x0080- DeviceType
R/--- string
Indicates the type of the connected device
0x00830x0084- SW-Version
R/--- string
Firmware version of the connected device
0x00850x0086- SerialNr
R/--- string
Serial number of the connected device
0x00890x00C0 Modbus_
R/W number
Modbus address of the BASICEVO. Once thisaddress
address has been changed, communication with
the BASICEVO can continue only via the new
address.
Table 5: Modbus register table•

R – Read Holding Registers (multiple)
Page 17

•

W – Write Single Register (single)

NOTE

All other registers not described here must not be changed under any circumstances.

7.1 Meaning of the individual bits in the status bit bar (SYS_Status):
Faults and error messages can be identified with the aid of the SYS_Status register according to thefollowing table.
Bit
Name
Value → Message
00---Without function (reserved)
01
WARMUP
1 → BASICEVO is in the warm-up phase (approx. 10 s)
02
SYS_ERR
1 → System fault
03---Without function (reserved)
04---Without function (reserved)
05
STARTUP
1 → BASICEVO is in the boot phase (approx. 40 s)
06
KORR
1 → Correction active (always)
07
MW_ok
1 → The zero point has been set
08---Without function (reserved)
09---Without function (reserved)
10---Without function (reserved)
11
MW_aktiv
1 → Averaging for drift correction is active
12
EEP_ERR
1 → EEPROM error
13
WDG_WRN
1 → After watchdog reset
14
POWER_ON
1 → Supply voltage switched on
15 OUT_OF_RANGE 1 → When “0x000A Conc” < -10% FS
or “0x000A Conc” > 110% FS
Table 6: Allocation of the error messages in the status bit bar SYS_Status

FS= (Full scale) upper range value
NOTE

The value 0 always stands for the (error-free) normal state.
The two bits 6 (CORR) and 7 (MW_ok) are internal flags set in the manufacturing process of theindividual BASICEVO. They are also used for quality control purposes and are set to the value “1” if
the respective BASICEVO had been temperature-compensated and was calibrated.

Page 18

7.2 Description of the unit code:
The Conc register (0x000A) provides a numeric value that varies in terms of its scaling and unit
depending on the BASICEVO version. The Unit register (0x004F) can be used to correctly calculate theconcentration value. The meaning of the numeric value in the Unit register (0x004F) is therefore
displayed as follows:
Register value
0
1
2
3
4
5
6
7
8

→
→
→
→
→
→
→
→
→
→

Unit / scaling
Unassigned, for special applications
ppm x 0.01
ppm x 0.1
ppm
Vol.% x 0.001
Vol.% x 0.01
Vol.% x 0.1
LEL x 0.01%
LEL x 0.1 %Table 7: Allocation of register value to the measuring unit and multiplier

NOTE

Partial quantities of < 1 vol.% are usually specified as a ppm value. The following table shows therelationship of vol.% to ppm:
Vol.%
ppm
100
1,000,000
10
100,000
1
10,000
0.1
1000
0.01
100
0.001
10
0.0001
1
Table 8: Relationship of vol.% to ppm

8

Information on start-up and operation

NOTE

We recommend the smartGAS Calibration Tool for setting the zero point and the end value. Thiscan be downloaded free of charge from the smartGAS homepage.
8.1 Self-test + warmup
After the BASICEVO sensor is switched on, an internal self-test is carried out and the green LED flashes.
After that, the sensor supplies measured values, and system errors are evaluated. After 40 seconds ofwarming up, the BASICEVO sensor outputs correct measured data.

NOTE

Correct measurement values are not output during the self-test.

Page 19

8.2 Setting the zero point
It is advisable to set the zero point• after reinstallation of the sensor or measuring system• at regular intervals (must be adapted to the application)• after repairs / maintenance work on the sensor or measuring system

NOTE

Before the zero point is adjusted, the sensor must be in operation for at least 30 minutes and a zerogas (e.g. N2 – 100 vol.%) must flow through the sensor until the indicator for the gas concentration
has reached a stable value.
If the aforementioned requirements are met, the value 1 is written in the register IR_4tagneu (0x0047)
and the zero point is thus reset.

8.3 Setting the end point
Setting the end point (also called final value or span calibration) requires the use of a test gas, whichshould correspond as accurately as possible to the upper range value of the sensor to be calibrated.
The same preconditions apply here as when setting the zero point: the sensor must be in operation for
at least 30 minutes and the test gas must flow through it until a stable value has been reached in theConc register (0x000A).
If all requirements have been met, the correction value for the respective measurement channel iswritten in the Span register (0x0054).
8.4 Calculating the correction value for the end point
Let us assume that a sensor indicates a concentration of only 978 ppm (called “Conc_old” here) whena test gas is applied which has the value 1003 ppm (called “Conc_cal” here).
Reading the Span register yields the value 9985 (called “Span_old” here).
The new calculation of the correction value for the Span register then takes place as follows:

Span_new = Conc_cal x Span_old / Conc_old
Span_new = 1003 x 9985 / 978 = 10240
The new value of 10240 is now written in the Span register (0x0054) and the process is complete!

NOTE

Always carry out a zero point adjustment with your smartGAS sensor first and then an end point
adjustment.
8.5 Restoring the calibration parameters to factory settings
To restore the calibration parameters to the factory settings, the registers “IR_4tagneu” and “Span”
can be rewritten. For this purpose, the register value from “fab_zero_value” must be written to“IR_4tagneu” and “fab_span_value” to “Span”.
Page 20

9

Annex

9.1

Mechanical dimensions [mm]Page 21

9.2 Operation of the BASICEVO on a microcontroller
For the BASICEVO to communicate with a microcontroller, the level of the signals at the module COM
pin must be adapted to the microcontroller. The easiest method is via an RS485 interface module thatmust be selected according to the microcontroller voltage supply.
The UART signals TXD (transmit data), RXD (receive data) and a signal for activating the transmitter
TXEN (transmitter enable) must be provided at the microcontroller. The following figure shows thecircuit:Figure 1: BASICEVO on a microcontroller

The circuit is designed for a microcontroller with 5 V operating voltage. When operating at 3.3 V, usean ADM3075 (or equivalent types) rather than the ADM4850 (or equivalent types). All othercomponents are unaffected.
Up to 16 BASICEVO can be operated in parallel with this circuit. This requires the devices to havedifferent Modbus addresses.
NOTE

It should be noted that BASICEVO must be connected to a power supply in addition to thecommunication connection shown above.

Page 22

9.3 Operation of the BASICEVO on a PC
Operating exactly one BASICEVO on a PC requires a special USB adapter incl. software; this can bepurchased from smartGAS as an accessory (article no. Z6-000025). The BASICEVO is powered via the USB
port; an additional power supply is not necessary. The following figure shows one such adapter:

Figure 2: USB adapter for operating a BASICEVO on a PC

9.4 Installation of the BASICEVO in a Modulbox with gas adapter
To adapt the BASICEVO with the calibration gases, the Modulbox illustrated below can be obtained fromus:

BASICEVO gas adapter (Z7-000001) and Modulbox (Z7-000004)

Page 23

10 Legal information
The figures and drawings used in this description may differ from the originals; they are provided solely
for illustrative purposes.
All information – including technical specifications – is subject to change without notice.
All pictures and graphics in this manual: © 2021 smartGAS Mikrosensorik GmbH, Heilbronn, Germany.

©2021 smartGAS Mikrosensorik GmbHsmartGAS Mikrosensorik GmbH |Hünderstr. 1 | 74080 Heilbronn | Germany
Phone: +49 7131/797553-0 | fax: +49 7131/797553-10 | www.smartgas.eu|mail@smartgas.eu
Edition 03/07_21
Page 24