smartIO 8x24

Description

The smartIO 8x24 offers connection options for 8 analog signal sources for voltage or current measurement with the following selectable measuring ranges:

• ±160V, ±80V, ±40V, ±20V, ±10V, ±5V
• ±200mA, ±100mA, ±50mA, ±25mA

Other key parameters are

• Sampling rate up to 1 kHz
• 24 bit analog-to-digital converter
• Common-mode voltage up to 100V
• Current input with overload protection
• Sensor linearization via polynomial
• Various filter options
• Isolation between process, supply and digital interfaces up to 1700 V DC

The module is configured via a serial interface (USB) and the extensive SCPI command set using any terminal program or, preferably, optiCONTROL. This configuration also includes the addresses, transmission rates and assignment of the CAN messages. Configuration in the field can be carried out via the CAN bus using the console application smiocan. This is part of the current versions in the Yocto-Linux of the smart family (smartMINI, smartRAIL, ...).

Each module is individually tested as a RAIL version with regard to dielectric strength and insulation between the process and USB side. The sturdy aluminum housing and the protective coating of the circuit board in accordance with EN50155 also meet the requirements for use on rail vehicles.

Even if the module is integrated in the smartRAIL housing, the connection for CAN and power supply is made via the two M12 connections. These can be connected in series with the smartRAIL connection using a short M12 connection cable.

optiMEAS reserves the right to make changes and errors in this and all other data, descriptions or examples relating to this product.

Function

The smartIO 8x24 has 8 inputs, each of which is are identically constructed:

• The connections of the voltage input (U_IN, COM) are each connected with a high impedance of $R_{\rm{in}} = 1 M\Omega$, an operating mode selector switch and the subsequent input amplifier with Sallen-Key filter (SKF).

• The connections of the current input (I_IN, COM) are connected to each other via a poly-fuse (PF) to protect against overload and a small shunt resistor $R_{\rm{Shunt}} = 10 \Omega$. The voltage is tapped at the shunt with a high impedance of $R_{\rm{in}} = 1 M\Omega$ and leads via the operating mode selector switch to the downstream input amplifier with Sallen key filter (SKF).

• The COM connections of the 8 channels are only connected to each other via the input impedances $R_{\rm{in}}$ and a virtual ground point. This means that the inputs are designed for differential measurement in every operating mode. The COM connection must therefore be set to a reference potential on each channel used.

• The common-mode voltage ¹ between the inputs may be up to 100V DC.

• The Sallen key filter limits the bandwidth of the input to 480 Hz and thus acts as an anti-aliasing filter for the subsequent AD converter.

• The AD converter based on the delta-sigma method is configurable up to sampling rates of 1 kHz, synchronous for all input channels. The programmable input gain enables different measuring ranges, the conversion width is 24 bit.

• A calibration data set is stored for each amplification and operating mode (U/I), which is used to calculate the measurement voltage or current at the input.

• This calibrated measured variable can be offset against a user polynomial² to map a sensor characteristic curve. This allows the module to output the physical measured variable of the sensor directly via CAN.

• This physical measured variable is fed to different filter stages in parallel:

  • a 1st order low-pass filter
  • a moving average filter
  • a moving RMS filter

The window width of the sliding filters and the time constant for the low-pass filters can be set together for all channels. With a window width of 300 samples, true RMS values for AC signals with the typical frequencies of 50 Hz (15 periods), 60 Hz (18 periods) and 16 2/3 Hz (5 periods) can also be measured directly.

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Communication

The measured values are transmitted on the CAN bus in individual messages. Up to 20 CAN messages can be configured with:

• CAN ID (11-bit, 29-bit)
• Transmission rate in ms, after device start or RTR
• Content

A large selection of data elements is available for the content, which includes not only the filtered measured values, but also status information on the channel, the internal temperature of the module, firmware and hardware status, or the physical unit. Preferably, the measured values are transmitted as a 4-byte <float>, which eliminates the need for further scaling on the receiver side if the module is planned and set up accordingly. Transmission as <int16> is also possible. In this case, however, the scaling of the output variable depends on the selected measuring range or the user polynomial in order to make the best possible use of the limited value range.

Configuration is carried out using an extended SCPI protocol via the serial interface³, which is available at the USB configuration port (COM, /dev/tty). The serial interface can be addressed with any terminal program⁴. The module adds an editable command input with history and offers an optional colored output. For certain commands that affect several channels simultaneously, the output is structured in a readable manner. In addition, the end of line used (CR, LF, CRLF) is determined automatically, thus enabling operation on a (classic) terminal. The `__?' command can be used to call up a detailed, documented list of all commands directly from the device. Critical commands are protected by a pass code. The configuration software optiCONTROL provides easy-to-use input masks for the essential settings to configure the module.

A service connection to the new smartIO family can also be established in the field via two reserved CAN messages (0x011, 0x012)⁵. An extended ISO-TP protocol is used via the messages. In addition to the actual data connection (ASCII/binary), asynchronous status information is also implemented for connection management and command processing on the device side. This makes it possible to select one device at a time for communication on the same CAN messages and to transmit even large amounts of data securely and bidirectionally. Furthermore, access protection is implemented using a seed key procedure.

About this service connection

• the SCPI command set of the device is used for configuration and
• a firmware update of the device software can be carried out.

In the current versions of the YOCTO environment, the smiocan console application can be used on the smart family devices to communicate via this service connection. The app offers the following options:

• Execute device search
• Set device time/date
• Various logbook outputs
• Commands from
  • the Linux command line
  • a batch file or
  • interactively
• Execute firmware updates for a specific or all devices

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Isolation of the connection groups

The input group for supply voltage and CAN bus, the USB configuration interface and the connections to the process are isolated from each other, suitable for systems with 110V nominal operating voltage up to an isolation voltage of 1.7kV DC.

Depending on the design of the module, process inputs are connected to each other with a high impedance to the internal analog reference point (virtual GND) and thus - usually negligibly - also to each other.

Interfaces of the module

Measurement inputs (X10)

Double-row Phoenix terminals with a 3.5 mm pitch are used for the measurement inputs [X10]. The position of pin 1 and the counting direction are marked on the housing.

Channel	I_IN	COM	U_IN
1	Pin 1	Pin 3	Pin 5
2	Pin 2	Pin 4	Pin 6
3	Pin 7	Pin 9	Pin 11
4	Pin 8	Pin 10	Pin 12
5	Pin 13	Pin 15	Pin 17
6	Pin 14	Pin 16	Pin 18
7	Pin 19	Pin 21	Pin 23
8	Pin 20	Pin 22	Pin 24

Suitable plugs from Phoenix are

• Art.-Nr. 1790399, DFMC 1,5/12-STF-3,5
• Art.-Nr. 1790580, DFMC 1,5/12-ST-3,5-LR

If several smartIO modules are used, the basic housing of the plug connection on the smartIO and the plugs can be uniquely marked using the coding profile. This makes it possible to pre-assemble the plugs and ensure a mix-up-proof connection.

• Part no. 1790647, CP-DMC 1.5 NAT - Coding profile

Voltage measurement

The U_IN and COM inputs must be used for a voltage measurement. The measurement is differential, both connections must always be used. The potential difference between different input channels must be within the range of the permissible common mode voltage.

In the configuration of the smartIO, deactivate the current measurement for the corresponding channel (adc:current N, 0) and select a suitable measuring range (adc:gain N, G). The optiCONTROL software is recommended for configuration; configuration via the SCPI interfaces is possible.

The following measuring ranges can be set:

Gain G	Measuring range
1	$\pm160\rm{V}$
2	$\pm80\rm{V}$
4	$\pm40\rm{V}$
8	$\pm20\rm{V}$
16	$\pm10\rm{V}$
32	$\pm5\rm{V}$

Current measurement

The inputs I_IN and COM must be used for a current measurement. The measurement is carried out differentially via the internal shunt resistor; both connections must always be used. The measurement can be carried out at any position in the supply circuit of the signal source (high/low side). The potential difference between different input channels must be within the range of the permissible common mode voltage.

In the smartIO configuration, activate the current measurement for the corresponding channel (adc:current N, 1) and select a suitable measuring range (adc:gain N, G). The optiCONTROL software is recommended for configuration; configuration via the SCPI interfaces is possible.

The following measuring ranges can be set:

Gain G	Measuring range
1	$\pm200\rm{mA}$
2	$\pm100\rm{mA}$
4	$\pm50\rm{mA}$
8	$\pm25\rm{mA}$

The scaling factors 16 and 32 are not calibrated and must not be used for measurements.

Sensor scaling

The measured input variables voltage or current are transmitted via the CAN bus with the factory settings in float format. Scaling to the measuring range used in the DBC file is not necessary. Scaling to the physical measured variable recorded on the sensor can be carried out in the DBC file or, better still, via the polynomial definition in the smartIO. The latter then also enables the correct display of the true RMS values that are calculated in the smartIO.

The following is an example of how to determine the coefficients for connecting a 4-20mA pressure sensor:

The polynomial to be determined specifies the relationship between the measurement signal $x$ (voltage or current at the measurement input) and the physical measured variable $y$ of the sensor:

$$\begin{array}{l} y(x) = Polynomial(x) = \sum\limits_{k = 0}^{n - 1} {{a_k}{x^k} = \ldots + {a_2}{x^2} + {a_1}x + {a_0}} \\ y(x) = \it{scale} \cdot x + \it{offset} \end{array}$$

The following information can be found in the sensor data sheet:

$$\begin{array}{l} \left[{\begin{array}{cc} {{x_{\min }}}&{{x_{\max }}} \end{array}} \right] = \left[ {\begin{array}{cc} {4{\rm{mA}}}&{20{\rm{mA}}} \end{array}} \right]\\ \left[ {\begin{array}{cc} {{y_{\min }}}&{{y_{\max }}} \end{array}} \right] = [\begin{array}{cc} { - 50{\rm{hPa}}}&{150{\rm{hPa}}} \end{array}] \end{array}$$

If you insert these points into the above equation, you get:

\begin{array}{l} \it{scale} = \frac{{y_{\max }} - {y_{\min }}}}{{x_{\max }} - {x_{\max }}}} = 12.5\frac{{hPa}}{{mA}}\\ \it{offset} = y({x_{\min }}) - \it{scale} \cdot {x_{\min }} = {y_{\min }} - scale \cdot {x_{\min }} = - 100hPa \end{array}

In this case, the following polynomial would be set in the smartIO for channel N=2:

adc:polynomial 2, 12.5, -100.0
adc:unit 2, "hPa"

The dialog-guided configuration using optiCONTROL is much simpler:

All result values on the CAN bus are then correctly scaled in hPa for this channel.

Power supply, CAN bus, configuration (X20 - X22)

Supply voltage and CAN bus are available on two M12 connectors (A-coded) [X20] and [X22] according to the Device-Net assignment. The 24V power supply and the CAN bus connection are looped through from the plug to the socket. to the socket. This means that several different smartIO modules can be modules can be connected in series. If no further smartIO module follows, the CAN bus is connected to a plug with an integrated terminating resistor (120 Ω) or directly to the Phoenix terminal. CAN-GND is identical to the supply ground is identical.

CAN In/Out (X20, X22)

The two connections [X20] and [X22] are internally connected 1:1 and functionally identical. The male/female pair design allows the CAN bus to be continued directly bypassing the smartIO.

Pin	Signal	Description
1	CAN shield	Cable shielding, is passed through
2	+24 V	Power supply +24V (nom., see technical data)
3	GND	Reference ground for power supply and CAN bus
4	CAN H	CAN bus: CAN high
5	CAN L	CAN bus: CAN low

Commercially available Device-Net cables that lead from socket to plug can be used. For pre-assembled cables, twisted pair cable bundles must be selected for connection pairs 2 and 3 as well as 4 and 5.

The smartIO itself does not have an internal terminating resistor for the CAN bus. This is available as an accessory in M12 format.

• Part no. 1507816, SAC-5P-M12MS CAN TR (Male)

• Part no. 1529344, SAC-5P-M12FS CAN TR (Female)

For information on setting up CAN bus networks and their termination, please refer to this article.

USB (X21)

Behind the USB-UART configuration interface [X21] is a USB-to-serial converter (CP2102N), which is mapped as a virtual COM port under Windows and as /dev/tty* and /dev/serial/by*... under Linux. This connection is also electrically isolated from the process level. The ASCII-based SCPI protocol is used to configure the module. However, the optiCONTROL software from optiMEAS, which provides a graphical user interface with appropriately prepared dialogs, is recommended for configuring the smartIO modules.

Certifications

EC Declaration of Conformity

The CE mark indicates compliance with the

• EMC Directive,
• RoHS 2011/65/EU (08.06.2011) and the
• Low Voltage Directive.

Railway applications-Electronic equipment on railroad vehicles, EN 50155:2017

Topic	Description	Standard
	For the smartRAIL version, in addition to the CE declaration of conformity, the following classifications and certifications for EN50155 are also provided:
	Environmental conditions: - AX (2000m) - TX (...) - Cold - Dry heat - Damp heat cyclic	EN 50125-1 §4.2.1 EN 50155 §4.1.2 EN 50155 §13.4.4 EN 50155 §13.4.5 EN 50155 §13.4.7
	Swinging Shock - Swinging - Shocking	IEC61373 §8 + 9 IEC61373 §10
	EMC + insulation Piece tests are carried out and recorded in accordance with EN50155 §12.2 - Visual inspection - Insulation 500V DC - Withstand voltage 1.7kV	EN50121-3-2 EN 61000-3-2/3 EN 55016-2-1/2 EN50155 §12.2.1 EN50155 §12.2.9.1 EN50155 §12.2.9.2
	Fire protection	EN45545-2

Technical data

Supply voltage / ambient conditions

Parameter	Comment	Min	Type	Max	Unit
Supply voltage	with reverse polarity protection	8	36	V
overvoltage protection		no
ESD protection	TVS diode		40	V
current consumption	@ 24V		50	60	mA
Connector	A-coded (M + F)		M12
Operating temperature	EN 50155 / range TX6	-40		85	°C
Relative humidity	(condensing)	5	95	%
PCB coating	EN50155		PC2
Housing			Aluminum
length	(without connector)		124		mm
width			85		mm
Height			35		mm
Weight			330		g
Cooling			passive
Protection class	ISO 20653			IP54
mounting	mounting rail (EN 50022)		TS 35
version RAIL
Insulation resistance	@ 500V	10		$G\Omega$
withstand voltage test	60s			1.7	kV

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CPU

Parameter	Comment	Value	Unit
Processor		ESP32-S3
Family		Xtensa® 32-bit LX7
Clock		240	MHz
ROM	FLASH	384	kB
RAM	SRAM	512	kB
data bus		32	bit

Analog inputs, digitization

Parameter	Comment	Min	Type	Max	Unit
Number	Voltage, differential7		8
Measuring range	Gain = 1	-160		160	V
	Gain = 2	-80		80	V
Gain = 4	-40		40	V
Gain = 8	-20	20	V
Gain = 16	-10	10	V
	Gain = 32	-5		5	V
Accuracy	$rms(\Delta U)/U_{\rm{Range}}$		0.02	% FS
input resistance	$R_{\rm{in}}$ to the virt. MP		1		$M\Omega$
number	Current, differential7		8
	Gain = 1	-200		200	mA
Gain = 2	-100	100	mA
Gain = 4	-50		50	mA
	Gain = 8	-25		25	mA
Accuracy	$rms(\Delta I)/I_{\rm{Range}}$		0.50	% FS
CM suppression	$\Delta c/c_{\rm{max}}$			0.05	% FS
Shunt	$R_{\rm{Shunt}}$, 1.5W6		10		$\Omega$
Poly-Fuse	32V, fast			500	mA
input resistance	$R_{\rm{in}}$ to the virt. MP		1		$M\Omega$
Anti-aliasing filter	Sallen-Key filter, 2nd order, switchable		480		Hz
Converter		Delta-Sigma		24
sampling rate			1000	Hz
Output rate	via CAN	0		1000	Hz
software filter	lowpass, 1st order	0		1000	ms
	MiWe, RMS		300	500	samples
Linearization	Polynomial	$a_0\cdot x^0$		$a_{14}\cdot x^{14}$

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Interfaces

Parameter	Comment	Min	Type	Max	Unit
Number	CAN 2.0 B			1
baud rate	parameterizable		500	1000	kbit/s
plug connector	A-coded (M + F)		M12
terminating resistor			no
number	Serial /USB		1
baud rate	fixed		38400		kbit/s
Connector			Micro-USB
Chipset	Supply by USB	CP2102N
Protocol			SCPI

Both interfaces are isolated from each other and from the measuring input.

The module responds to the SCPI request *idn? with an identification according to the following pattern, whereby the serial number, version status and date/time stamp will vary:

optiMEAS, smartIO, 8X24, 1, 24006200011, 1.35, 0, Nov 22 2024 15:50:07, 20240610

Process image

The following messages are reserved for the smartIO family with ESP controller:

CAN-Id (dec)	CAN-Id (hex)	Data type	Direction	Description	Unit
16	0x010	uint48	to all smartIO	timestamp (Unix, 1970-01-01)	ms
		uint8		0
		uint8		Checksum
17	0x011	ISO-TP+8	to all smartIO	Diagnostic interface
18	0x012	ISO-TP+8	from activated smartIO	diagnostic interface

The process image for measurement data and status information is freely configured via the SCPI interface. With the factory settings, the following messages and content are sent in Motorola format (MSB) with a baud rate of 500kBit:

can:msg 0x0F0, -2, 9000, 9001, 9002
can:msg 0x0F1, 10, 0, 1
can:msg 0x0F2, 10, 2, 3
can:msg 0x0F3, 10, 4, 5
can:msg 0x0F4, 10, 6, 7
can:msg 0x0F5, 100, 200, 201
can:msg 0x0F6, 100, 202, 203
can:msg 0x0F7, 100, 204, 205
can:msg 0x0F8, 100, 206, 207
can:msg 0x0FD, 1000, 8000, 8001, 8002, 8300, 8301, 8110

CAN-Id (dec)	CAN-Id (hex)	Param.-ID	Data type	Output clock	Description	Unit
240	0x0F0	9000	uint40	Startup + RTR	Serial Number 240062#####
		9001	uint8		HW Version
		9002	uint16		SW Version	$\cdot 0.01$
241	0x0F1	0	float	10 ms	Input 1, PT1-Filter	V, mA, X
		1	float		Input 2, PT1 filter	V, mA, X
242	0x0F2	2	float	10 ms	Input 3, PT1 filter	V, mA, X
		3	float		Input 4, PT1 filter	V, mA, X
243	0x0F3	4	float	10 ms	Input 5, PT1 filter	V, mA, X
		5	float		Input 6, PT1 filter	V, mA, X
244	0x0F4	6	float	10 ms	Input 7, PT1 filter	V, mA, X
		7	float		Input 8, PT1 filter	V, mA, X
245	0x0F5	200	float	100 ms	Input 1, RMS[300]	V, mA, X
		201	float		Input 2, RMS[300]	V, mA, X
246	0x0F6	202	float	100 ms	Input 3, RMS[300]	V, mA, X
		203	float		Input 4, RMS[300]	V, mA, X
247	0x0F7	204	float	100 ms	Input 5, RMS[300]	V, mA, X
		205	float		Input 6, RMS[300]	V, mA, X
248	0x0F8	206	float	100 ms	Input 7, RMS[300]	V, mA, X
	207	float		Input 8, RMS[300]	V, mA, X
253	0x0FD	8000	uint8	1000 ms	CPU0 load	%
		8001	uint8		CPU1 load	%
		8002	uint16		PCB Temperature	0.1 °C
		8300	uint8		Status SK filter, `bool[8]
		8301	uint8		Current-Modes, `bool[8]
		8110	uint16		Missing ADC cycles

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Footnotes

1. Based on the average voltage potential between U_IN or I_IN and COM. ↩

2. Polynomial up to $a_{14}\cdot x^{14} + ... a_2 \cdot x^2 + a_1 \cdot x + a_0$, the polynomial is calculated according to the Horner scheme ↩

3. 38400 baud, 8 data, 1 stop, no parity, [x] Local Echo, [x] Implicit CR with LF (receive) ↩

4. E.g. PuTTY or TeraTerm - these are not part of the scope of delivery ↩

5. The addresses used represent the optiMEAS standard for the administration of the smartIO family. They can be changed for special areas of application in order to avoid collisions with existing communication protocols. These messages are free in the CANopen standard. ↩

6. The measured currents are converted directly at the shunts into a corresponding heat output of up to 0.4W / channel. If all channels are operated constantly at 200 mA, an additional heat output of 3.2W is generated on the module! Although this is tested and permissible as a continuous load, it leads to a significant heating of the entire module depending on the ambient conditions. No negative effects are to be expected for typical measurement operation with dynamic measurement signals. ↩ ↩²

7. Either the voltage measurement or current measurement operating mode must be selected for each input. ↩ ↩²

8. For the diagnostic interface, the ISO-TP protocol is extended by the type code 0xE0 for the Connection Management Layer (CML). The data packets have a length of 1 to 8 bytes, depending on their content and function. ↩ ↩²