Picowatt AVS-47B User Manual

PICOWATT

Veromiehentie 14
FI-01510 VANTAA, Finland
phone [phone]

Internet: www.picowatt.
e-mail: reijo.voutilainen@picowatt.

AVS47-Serial/USB-W CONVERTER

For Interfacing the AVS-47B with Computers

User Guide

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User
Guide 1R3

For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

(for use with rmware version avs47_serial_usb_1r3.ino)

CONTENTS

WARRANTY 3

BACKGROUND 4

USB-Picobus 4
GPIB-Picobus 4

AVS47-Serial/USB-W 4

CONNECTING THE AVS47-Serial/USB-W 5

STARTING THE AVS47-Serial/USB-W 6

Resetting the AVS47-Serial/USB-W 6

RS232 Format 6

COMMANDS AND COMMAND LINES 7

Responses 7

Send/Receive Serial tool 9

FIRST COMMANDS AND QUERIES 10

HARDWARE COMMANDS 10

MEASUREMENT AND READOUT
COMMANDS/QUERIES 11

OTHER COMMANDS AND QUERIES 14

COMMANDS FOR THE TS-530A
TEMPERATURE CONTROLLER 16

CABLE SPECIFICATIONS 18

Picobus Cable (PB25P15P6W5M) 18
Serial Cable (RS9P9S3W1.5M) 18

RE-PROGRAMMING THE AVS47-Serial/USB-W 19

AVS47-Serial/USB-W TROUBLE SHOOTING IDEAS 19

DECLARATION OF CONFORMITY 22

INDEX 23

REVISION HISTORY 25

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AVS47-Serial/USB-W CONVERTER

WARRANTY

Picowatt warrants the AVS47-Serial/USB-W
hardware to be free from defects in materials and

workmanship. Our liability under this warranty is
limited to repairing or replacing any instrument or
part thereof which, within three (3) years after the
shipment to the original purchaser, proves defective.
This warranty is void if the instrument has not been

used according to the instruction manual, or if it has

been used under exceptional environmental condi­tions.

In need of warranty repair, the instrument must

be returned to Picowatt, prepaid , and with a detailed

description of the fault or malfunction following the

instrument.

The name, address and e-mail address of a person

who is able to give supplementary information should be
included whenever possible. If the repair was covered
by warranty, Picowatt will return the instrument on
our cost using an economical shipping method.

If no fault is found, or if there is a strong indication

that the warranty is void, the purchaser is charged for
the return freight and costs in addition to the repair. It
is recommended that Picowatt be contacted prior to
shipment. We can possibly give instructions for addi-

tional tests or simple component replacements so that

unnecessary shipments may be avoided.

The rmware must not be considered a com-

mercial product. It is given as is, for free, without

any kind of warranties or liability. The program and
this user guide may contain errors, and we would be
glad to get feedback, corrections and suggestions for
improvements.

Important: The AVS-47B uses +/- 5 Volt levels for data communica­tions in its standard conguration, whereas the AVS47-Serial/USB-W
can be damaged by applying negative voltages to its 15-pin connec­tor.

Therefore, short circuit piece JP204 MUST BE CHANGED to

position JP203 on circuit board “E” (the board with the power supply
unit) before connecting the AVS-47B and the converter together. In
case of any uncertainty, please contact factory.

If the AVS-47B is interfaced with model AVS47-IB GPIB box, or directly with a PC com­puter using its Com port or via a USB-232 adapter, this jumper shall be returned to JP204.

RV-Elektroniikka Oy Picowatt
Veromiehentie 14
FI-01510 VANTAA
FINLAND
telephone [phone]
email: reijo.voutilainen@picowatt.

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

BACKGROUND

The AVS47-Serial/USB-W is an external protocol
converter that creates an galvanically isolated RS232

interface for the model AVS-47B AC Resistance

Bridge. Until now, Picowatt have offered two possi­bilities for interfacing the AVS-47B with computers:

The direct Picobus interface and the Model AVS47-
IB external GPIB (IEEE-488) interface unit. Both al-

ternatives have limitations with respect to computer
type, operating system and programming language.
The AVS47-Serial/USB-W removes many of these
limitations at a low cost, offering new possibilities
for computer interfacing. A short comparison of the
three available interfacing solutions follows.

Some commands are for the TS-530A Tempera­ture Controller. This product has been discontinued,
and those features are only for the existing instru­ments.

USB-Picobus

Picobus is a proprietary synchronous, serial pro-

tocol that is based on two coming and two leaving
signal lines. Suitable four lines are provided by the

hardware handshake outputs and inputs of traditional

Com: ports of PC-type computers. The asynchro­nous TXD and RXD signals of the RS232 interface
are not used by Picobus. Today’s computers seldom
have physical Com: ports, but a virtual Com: port
can be created by a USB-232 converter.

Unfortunately, low-level Picobus communica-

tion is complicated, as it requires computer program

to write and read states of independent bits of some
hardware registers. In order to make programs port­able between different platforms, operating systems
do not favour direct hardware access. For this rea­son, we offer driving programs (USB-Picobus), but
only for a Windows-PC running LabView2012 or
higher (base version or better).

This has been a serious limitation that excludes
Mac computers and programming languages other
than LabView. The great advantages of Picobus are,
that the protocol is almost bullet-proof, it has low
EMI noise, and for customers with a suitable com­puter environment, it is completely free with the
exception of a possibly needed USB-232 converter.

GPIB-Picobus (OBSOLETE!)

This interfacing solution is based on an external con­verter, AVS47-IB, between IEEE-488 and Picobus
protocols.

This very powerful converter offers automatic
scanning of sensors, buffering of data and many
macro commands. The box is connected to - but gal-
vanically isolated from - the AVS-47B via Picobus
and to the computer via GPIB (therefore the name of
this option is GPIB-Picobus). It has its own mains
power supply and it can be located far from the cry-

ostat in order to minimize electromagnetic or ground

current problems that the GPIB line may cause. The
box can be used with computers having an GPIB
controller and suitable software for GPIB communi­cations. It is highly compatible with the IEEE-488.2

standard with its mnemonic and common com-

mands and error reporting. We offer a versatile free
LabView Driver that was written for LV7.1 and can
still be used with today’s LabView versions. For the
most noise-critical applications, an optical bre link
to the bridge is available (AVS47IB-PICOLINK).

The GPIB-Picobus had a much wider range of
applications than USB-Picobus, e.g. it can be inter­faced also with Mac and Linux computers. How­ever, for customers that do not already use GPIB, the
cost of this alternative is signicant.

AVS47-Serial/USB-W

The AVS47-Serial/USB-W is also an external proto-
col converter box that is connected to the resistance
bridge via galvanically isolated Picobus. It can be
connected to the computer’s Com: port using a one-

The AVS47-IB is a protocol converter between GPIB
(IEE-488) and Picobus. It is the heart of the “GPIB­Picobus” interface.

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AVS47-Serial/USB-W CONVERTER

to-one cable with 9-pin connectors. More typically, it
is connected to a virtual RS232 port using a USB-
232 converter which enables RS232 communications
between the computer and the box. The important
difference between USB-Picobus and AVS47-Serial/
USB-W is that the former uses the proprietary syn­chronous Picobus protocol and the latter is based on
asynchronous RS232.

RS232 is a very old protocol which has disap­peared from many instruments because of its low
speed and poorly standardized software behaviour.
However, asynchronous serial communications is far
from dead: Most operating systems, like Windows,
Linux and Mac OS, and most common programming
languages, like C/C++, Python, versions of Basic
etc., LabView and Matlab, support it. The speed is

not an issue with slow instruments, like the AVS-

47B, which produce only tiny amounts of data. The
AVS47-Serial/USB-W expands computer-interfacing
of the AVS-47B beyond a Windows-PC and Lab­View to almost any application and platform where
RS232 communications is supported.

Commands and queries to the AVS47-Serial/

USB-W are simple and mnemonic, like “RAN3” for
the 200Ω range. Communications is based on the
most common default format without handshaking.
Therefore many low-cost USB-232 converters are
likely to perform well in this application.

The AVS47-Serial/USB-W is based on the very
popular Arduino Mega2560 unit.

AVS47-Serial/USB-W Unit measures 130x105x60
mm and gets power from the +12V Mains Adapter.

CONNECTING THE AVS47-Serial/USB­W

The AVS47-Serial/USB-W is connected to the AVS­47B Resistance Bridge using the supplied 5-meter

long DB25P/DA15P cable. The AVS47-Serial/USB
box should be located near to the computer and far
from the cryostat. Connection from the box to the
computer varies depending on available hardware:

- Computer has a physical RS232 port:

Connect the supplied 1.5m cable with male and
female 9-pin D-connectors from the AVS47-Serial/
USB-W box to the RS232 port of your computer.

- Computer has only USB ports:

You need a USB-232 converter and its software
installed. Plug the USB connector to your computer
and the our supplied 9-pin cable between the con-

The AVS47-Serial/USB-W uses 0/+5V
voltage levels for communications with the

AVS-47B Resistance Bridge, which is set for

-5/+5V levels by default. Therefore, open

the top cover of the bridge and move short
circuit piece JP204 to position JP203 before
making any connections (“E” board).

The jumper must be in position JP204 if

AVS-47B is interfaced with an AVS47-IB or

directly with a PC computer, or with a USB­232 adapter

Change short circuit piece JP204 to position JP203
before making any connections in order to avoid dam­age to the AVS47-Serial/USB-W, which uses 0/+5V
voltage levels for communications with the AVS-47B
resistance bridge.

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AVS47-Serial/USB-W CONVERTER

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There are two ways to connect the AVS47-Serial/USB-W: Either directly to
computer’s RS232 port, or via a USB-232 converter to computers USB port.
The converter creates a virtual RS232 port that your high-level program will
access.

verter and the AVS47-Serial/USB box. The USB-
232 converter from National Instruments (NI part
number 778472-01) is known to work well, but it is
expensive. Cheaper converters are available from
other manufacturers. Check their compatibility with
your platform.

STARTING THE AVS47-Serial/USB-W

The box starts when it gets power from the +12V
DC adapter. The “REMOTE” indicator on the AVS­47B front panel is blanked but indicates booting by
blinking weakly once. The box starts always in local
mode. Change from local to remote or vice versa
does not alter the state of the bridge.

Resetting the AVS47-Serial/USB-W

If needed, the box can be re-initialized by unplug­ging and re-inserting the 12V power plug. This
operation does not change the states of the bridge
or the TS-530A controller. However, you must then
re-program the settings of the TS-530A with the last

used values, which must be in computer’s memory,
as they cannot be read from the old temperature
controller.

Before sending any query to the box, refer to
command TER on page 10 and use it for instructing
the box to send a line terminator that your computer
program expects.

The box can be reset by command “RST”. It will
bring the bridge to a safe setup: input=ZERO, multi­plexer channel=0, range=2MΩ, excitation=3µV and
display=R. In addition, command separator defaults
to “;” (semicolon) and response line terminator to
CRLF. Software reset is a less powerful way to ini­tialize the program than the power-off-on method.

RS232 Format

The AVS47-Serial/USB-W uses the most common

RS232 format: baud rate 9600, 8 data bits, no parity,
1 stop bit and no ow control. This format can be
changed only by changing the Arduino rmware
source code and uploading it. Do not change this
format, if there is no compelling reason to do so.

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AVS47-Serial/USB-W CONVERTER

COMMANDS AND COMMAND LINES

It is a good idea to get acquainted with the

AVS47-Serial/USB-W by using an RS232 hyperter­minal program. It lets you control the bridge by writ­ing commands/queries and reading the responses.

Although such a program is no longer included in

Windows, many free programs are available from
the Internet. For example, we have used

https://sourceforge.net/p/hypetermi-

nal/wiki/Home/

and, if you have LabView, you can try

https://decibel.ni.com/content/docs/

DOC-16284

See also page 9.

Commands to the AVS47-Serial/USB-W are not case

sensitive. You may insert blank space(s) between the
command and argument part. Commands “ran5”,
“RAN5”, “ran 5”, “RAN 5” or “ran 5” are all
equivalent.

The rst part of a command or query can contain

only alphabetic letters. The second, argument part of

a command, is made of integral numbers. The argu­ment part of a query is a question mark “?” like in

“RAN ?” or “ran?”.

Several commands can be placed on a single
command line. The commands/queries must have
a command separator, or delimiter, between them
(comma or semicolon, which is the start-up default).

Your own computer program can terminate the com-

mand line either by carriage return (CR or \r, ASCII

13), by linefeed (LF or \n, ASCII 10) or by CRLF.
These are called line terminators and the box recog­nizes them all. The commands/queries are performed
in sequential order, the previous command must be
completed before the next one can be handled.

For example: “rem1;inp1;ran3;exc7” (quota­tion marks are not parts of the actual string) sets
the bridge in remote mode, sensor measuring input,
200Ω range and 10mV excitation. After having
waited for some seconds (settling time), one can take
the reading.

Maximum number of characters on one line,
including command separators and possible blanks,
is 255. Handling the commands starts after a line
terminator has been received. If the command line

is not terminated with CR, LF or CRLF, processing

will not start.

Do not issue further commands or queries before
all the commands/queries on the previous command
line have been executed.

Responses

The AVS47-Serial/USB-W obeys the principle, that
only a query can produce response. So your applica-

tion program needs not poll and read the serial port

after commands.

The only exception to this is the REPEAT com­mand. If the repeated line contains queries, the
responses are sent automatically, and you must
decide how to read them. It is not necessary to read
responses, the buffer is emptied after each repeated
line.

Responses can consist of printable alphanumeric
characters, but most queries return only a number.
Some values are output as oating point numbers,
but exponential format is not supported. The re-
sponses do not have headers in order to make them
easier to read into a program.

If a command line consists of more than one

query, the responses are output in the corresponding
order and they are separated by the specied com­mand separator (delimiter).

For example, command line
“ARN10;RES5;RES?;RAN?” instructs the bridge to
go to autorange mode, wait for 10 seconds after each
automatic change of range (if needed), then take a
mean of 5 A/D conversions, and place the result and
the range setting (which was possibly altered by au­toranging) in the output queue. The result is sent via
the RS232 port to the computer, which must detect
that data has arrived into the serial buffer and then
read it from the buffer. The response could be like
“1234.5000;4” (i.e. 1234.5Ω; 2kΩ range).
You may save programming overhead by giving

commands for a measurement on one line. Respons-
es to queries may be easier to read into variables, if

queries are made separately for each item. Then one
does not need to remove the delimiters and parse the
response line.

The response ends by the line terminator speci­ed by the TER command (default is CRLF). The
terminator can, but it must not, be the same for
both transmitting and receiving. The AVS47-Serial/
USB-W will always recognize any of the three line
terminators, CR, LF or CRLF.

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AVS47-Serial/USB-W CONVERTER

The “Hype! Terminal” (see text for link) is easy to use: Just specify the Com port number (SetUp) and it is ready. After identica­tion, the bridge is set for measure input, channel 0, range 2kΩ, and excitation 300µV. Then 10 A/D conversions are taken (RES10)
and the output is read by RES?. This RS232 terminal program for a Windows PC does not require LabView.

Users of LabView can also try this program (see text for link). The output includes all printing and
non-printing characters in both transmitted and received strings, which can be useful for debugging. But
otherwise it is far less convenient to use than the previous example.

Send/Receive Serial tool

This handy LabView VI was written for developing
programs for the AVS47-Serial/USB-W. It allows

one to send commands and queries and to read the

response to queries. It requires the base version or
better of LabView2012 or later.

Check the jumper position JP203 inside the AVS­47B bridge and connect the cables as was instructed
earlier. The AVS47-Serial/USB-W starts when it gets
power from the +12V mains adapter. Select the cor­rect Com port. The serial format is xed to the most
common default, 9600,8,N,1 with no ow control.
Run the VI and click “SEND” for sending the de­fault IDN? query. DATA IN BUFFER should light.
Click “RECEIVE” for reading the response. If this
works, make the port number default and save the VI
so that you do not need to re-enter the port number
when you load the VI next time.

Use this tool for getting acquainted with the be­haviour of the software before starting to write your
own application in whatever programming language
you prefer. Labview programs recognize only ‘\n’

(newline) character for terminating the transmitted
string, but some other program may expect ‘\r’
(carriage return) or \r\n. Dene the response line
terminator by the command TER.

You can see the non-printing characters in the

response if you stop the VI, click the RESPONSE
eld and select ‘\’ Codes Display or Hex
Display from the context menu. Start the VI
again.

If you try to receive before a response is avail­able, the program waits until the input buffer is
non-empty or timeout occurs. See the block diagram,
how this was done. You can put the OPC? query
after a time-taking command like a long average
(e.g. RES100;OPC?). The “operation complete”
query places character ‘1’ in the output queue when
averaging is ready. You do not need OPC?, if you
have only one query and put it as the last item on the
command line.

This VI can be downloaded from our WEB site at
http://www.picowatt./interfacing/computer_inter­faces.html (“read and write using LabView”).

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HARDWARE COMMANDS

INP [0..2 | ?] Input selector command/query.

0 = Grounded input (zero resistance)
1 = Measure the selected sensor channel
2 = Calibrate (bridge measures internal 100Ω)
INP? returns 0..2

MUX [0..7 | ?] Multiplexer channel command/

query. The bridge will need a settling time after
channel has been changed. The required time
is longer if excitation is low. Use the DLY

or SCK command after setup commands like

MUX, RAN and EXC, before starting to take
readings.

0..7 = sensor channel
MUX? returns 0..7

RAN [0..7 | ?] Range command/query

0 = no range is connected. No excitation can
run into the sensor, and output is random. Do
not use this value in order to avoid accidental

heating of the sensor when another range is

later selected. If you do not know the proper
range, start from 2MΩ.

FIRST COMMANDS AND QUERIES

All queries work in both remote and local modes,
so that you can read bridge settings although it is in
local. Commands that control the operation of the
AVS47-Serial/USB rmware are also effective in
both modes, whereas hardware commands to the
AVS-47B can be used only in remote. These initial

commands are for making the AVS47-Serial/USB

rmware to correspond to your application program.

The commands and responses are same for the -W

and -F versions.

IDN?, *IDN? Identication query. You can check

succesful starting and rmware version of the
AVS47-Serial/USB by this query. The response
has four comma-separated elds and is like
“PICOWATT, AVS47-Serial/USB,0, REV
1R3”. The serial number eld is identically
“0”.

HW? Hardware version query. Returns the ver-

sion of the AVS47-Serial/USB hardware. The
response is like “PICOWATT, RS232PB_A2”.
The latter item is the version of the mother
board.

AL? Alarm line query. This query transacts with

the AVS-47B bridge and checks the state of
the “AL” Picobus signal line (AL is used for
preventing multiple reads of a single A/D con­version). Response should be 1 if the bridge is
powered, if the 25/15 pin cable is in place and
everything is OK. If the response is 0, check
that the cable is plugged and OK. Re-start the
box by re-connecting its +12V power. The
bridge should end up in local mode. If AL?
still returns zero, refer to the trouble-shooting
procedure (pp. 20) or contact factory.

LIM [0..1] Select the command delimiter (or com-

mand separator).

0 = semicolon (dec ASCII 59). This is the start­up default, which is used also by the IEE-488.2
standard.

1 = comma (dec ASCII 44). May be useful if a
comma-separated format (CSV) is preferred.

TER [0..3] Select the response line terminator

that the box uses for indicating the end of
its response. Depending on your computer
software, you may need to modify the default

value of CRLF. When reading the serial port,
the AVS47-Serial/USB rmware looks for both

CR and LF, and when either of them is en-

countered, the line is considered as ended. The
possibly remaining terminator is neglected.
You can modify the response line terminator by
sending the TERx command:

0 = nothing
1 = linefeed (LF, \n, dec ASCII 10)
2 = carriage return (CR, \r, dec ASCII 13)
3 = CRLF (start-up default)

REM [0..1 | ?] Remote mode command/query. The

change from local to remote does not change

the state of the bridge: the program rst reads

the setup in local mode and then sends this

setup to the bridge in remote mode. Any
hardware commands sent before the REM1
command are forgotten. The AVS-47B shows
remote mode by a yellow light on the front
panel.

0 = local
1 = remote

REM? returns 0 or 1

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

1..7 = ranges from 2Ω to 2MΩ
RAN? returns 0..7

EXC [0..7 | ?] Excitation command/query. Excita-

tion voltage, as the term is used in the context
of the AVS-47B, means the RMS voltage
across a sensor whose value is half of the se­lected range. Excitation is symmetrical square
wave -shaped current at about 13.7Hz.

0 = no excitation

1..7 = 3µV, 10µV, 30µV...3mV
EXC? returns 0..7.

REF [0..20000] Reference command for

deviation (ΔR) measurements. For example,
REF10000 sets the AVS-47B’s reference DAC
to 1 Volt, which corresponds to the middle of
any currently selected resistance range.

The resulting DAC voltage can be measured
by switching the ADC input to DIS3 (the
internal reference). Then issue ADCx for
measuring the output voltage of the DAC.

The programmed reference DAC has only 12
bits (0..4095), whereas the 0..20000 output of
the bridge corresponds to about 14 bits.The
reference value is therefore divided internally
by 5 for scaling it to range 0..4000. The DAC
output changes in steps of 5 digits (500μV)
and has a typical accuracy of a low-cost 12-bit
D/A converter.

NULDEV [1..100] Null deviation command.

This is a macro command that measures

whatever was previously selected by the DIS
command and then sends this value to the
reference DAC. The argument determines,
how many A/D conversions are used for the
measurement. A longer average improves ac­curacy if readings are noisy.

This command is intended to be used only
with DIS0. The REF POT / REF MEM front
panel switch must be in REF MEM position.
After the NULDEV command, the rear panel
DIFFERENCE BNC output is near to zero.
Select DIS1 for measuring the difference.

RFS? Reference source query.

The deviation signal VdR, is the difference
between measured resistance value (analog

voltage from the self-balancing circuitry) and
the reference voltage. The reference voltage,
in turn, can be either the output voltage from
the reference DAC or the voltage of the front
panel potentiometer. This selection is made by
the front panel REF POT/REF MEM -switch.

There is no remote command for changing the

switch position.

The reference DAC is programmed remotely
by sending the REFx command (see above). It
can also be programmed manually by lifting
the SET REF switch momentarily. Then the
DAC takes the displayed reading as input. De­viation can be nulled this way manually. The
NULDEV command is for making it remotely.

In remote-controlled applications, the refer-

ence-source switch should be in REF MEM
position. You can verify this by quering RFS?.

The response is:

0 = reference DAC (reference memory)
1 = front panel potentiometer

MAG? Magnier query

The deviation voltage VdR can be amplied by
a factor of 10. Amplication is made by a sim­ple circuit and is therefore not very accurate.
The ΔRx10 mode is suitable for recording
only small changes, not for measuring abso­lute values. It is best when excitation is high
and readings therefore less noisy. Magnica­tion can be selected only manually. MAG?

returns

0 = 1xΔR
1 = 10xΔR

MEASUREMENT AND READOUT
COMMANDS/QUERIES

These commands are for determining the A/D con­verter input, for making single or averaged A/D con­versions, and for reading the result. There is also a
command for detecting the possible ADC overrange.

DIS [0..7 | ?] Display selector command

This command selects one of 8 possible volt­ages to be measured. The current selection can
be queried by DIS?.

Use the RES command and query only when

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

displaying DIS0 and DIS1. The RES? query
can also be used for reading item 7 (Set point
of the old TS-530A temperature controller).
Then you get the set point in resistance, scaled
correctly by the currently selected measur­ing range. However, because of the very old
design, the TS-530A set point cannot be given
in resistance but it must be given as an integer.
Refer to the “SPT” command below.

Use the ADC command and query for all
other display items than 0,1 and 7 because
the RES values are scaled by the currently
selected measuring range. The ADC? query
returns integers -19999..19999 corresponding
to its input voltages from -2V to +2V. Refer

to the AVS-47B manual for how to use the

various display items.

0= Voltage proportional to the sensor value R
1= Deviation ΔR between R and the reference
2= Adjust reference. This is the voltage from

the front panel potentiometer

3= Reference. This is output voltage from the

reference D/A converter

4= Excitation voltage. This is the approximate

excitation voltage across the sensor. Useful
only on the lowest resistance ranges and
high excitation. Can be used for estimating
current lead resistance.

5= 530A heater voltage, (amplied inside TS-

530A, negative reading)

6= TS-530A heater current (actually, voltage

across current sense resistor in volts)

7= TS-530A set point voltage (V).

ADC [1..1000 ] A/D conversion command

The A/D conversion is made from voltage that
has been previously selected for measurement
by using the DISn command. The ADC com­mand can be used both in local and remote
modes.

ADC1 makes one single measurement, ADCn
makes n successive measurements and cal­culates their average. Conversions take 0.4
seconds each, rate is 2.5 conversions/second.

If the result is an exact zero, the conversion is
automatically repeated for detecting possible
overrange (because the ICL7135 ADC yields
a blinking zero in case of an overload.

ADC? A/D conversion query

This query returns the mean value of n con­versions (see above). The conversion result
is given as an integer -19999 to 19999 for
ADC input voltages -2V..+2V. Polarity is
indicated by minus sign and it is also returned
by the POL? query. Use ADCn and ADC? at
least for measuring items 4..6, which are not
directly dependent on range. Use RESn and
RES? for measuring intems 0, 1 or 7. Items 2
and 3 can be measured using either command.
If the ADC’s range is exceeded the result is an
exact zero, which can be distinguished from a
real zero by checking OVR? See also OVR?
and ARN.

ADC? query can be preceded either by an
ADCn or RESn command. They are one and
the same function. The result is valid until the
next ADC/RES command.

RES [1..1000] A/D conversion command for

resistance.

The ADC reading is scaled by the currently

selected resistance range, therefore measure-

ment of display items 4-6 can produce mis­leading results.

RES1 makes a single conversion, RESn
makes n successive measurements at 0.4
second intervals and their mean value is calcu­lated.

If the A/D converter outputs an exact zero, the
conversion is automatically repeated for de­tecting a possible overload. The OVR? check

should be a routine part of your application
program.

RES? Query for resistance

Resistance is output as a oating point number
with four decimal places for R and ΔR dis­plays, and with ve decimal places for 10xΔR
display. It is scaled by the currently selected
resistance range. The reading may include
a preceding minus sign. Arduino Mega2560
does not support output in exponential form.

RES? query can be preceded either by an
ADCn or RESn command, they are actually
one and the same function. The result is valid
until the next ADC/RES command.

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

POL? Polarity query

The ADC? and RES? return values are preced­ed by a minus-sign if the reading is negative.
You will probably not need this query, it is
used by the rmware. POL? returns
0= negative
1= positive

OVR?, OVL? Overrange query.

An overrange-reading from the ICL7135 ADC
is an exact zero, which can be distinquished
from a true zero by repeating once each meas­urement that yields an exact zero. A BUSY bit
from the A/D converter alternates if over­range, which separates these two cases. The

AVS47-Serial/USB does this check automati-

cally.

If a single A/D conversion is made by using
ADC or RES command and the result is over­range, the ADC? reading is coerced to 20001
and the RES? reading is coerced to 2000100.0
which both are impossible readings in normal
operation. In addition, the OVR? bit is 1 and
ERR? is “ADC overload”.

If n in ADCn or RESn is greater than
1, the average may contain one or more over­range- readings. No coercion is made, as the
average can still be useful. Overrange detec­tions are internally OR’ed together. OVR?=1
then indicates that the nal average contains at
least one overrange reading (which is 0). Such
an average is distorted and perhaps it should
not be used.

If there is any possibility for such a situa­tion, use autoranging. It will react to the rst
overranged conversion and, after autoranging
and autoranging delay, averaging is re-started.
This quarantees a correct mean value.

OVR? returns:

0= no overrange
1= reading was overrange, or at least one sam­ple in the average was overrange.

OVR? gets information from the A/D conver­sions. Do not use OVR? alone without a pre­ceding ADCx conversion command. Instead,
reading the conversion result is not necessary
for asking OVR?.

MIN?, MAX? These queries return the minimum

and maximum resistance values (in ohms) of

conversions averaged for one RESn or ADCn
command.

STD? Standard deviation of the averaged A/D

conversions as resistance in ohms. Use a long
average for getting a reliable STD. If noise is
purely random and white, STD is proportional
to the noise at the bridge input. If data has a
trend, STD is not useful.

QRATIO? This is simply (MAX-MIN)/STD. For

a purely random white noise, QRATIO is
about 5. A much higher gure may tell about
external interference in data, whereas a much
lower gure can tell about insufcient number
of samples. QRATIO is also affected by the
digitising step if excitation is high. It is most
useful at low excitations.

REPEAT This command repeats one command

line continuously. The commands and queries
behave excactly similarly as if only one line
were sent. If the line includes queries, the
CPU sends responses automatically and your
program can read them as they come. This is

an exception to the rule that the CPU does
not send anything by itself, without an explicit
query. Repeating is stopped by sending any-

thing via the RS232 line. An example using a
hyperterminal program:

ADC5;ADC?;REPEAT

response:

12345
12346
12344 etc.

The REPEAT command must be the last item
on a command line. In the repeating state,
the bridge gives new readings 2.5 times/sec­ond. Your application program can read all
responses as they come, or you can read only
when readings are needed. There is no buffer
for saving old results in the CPU.

Stop continuous repeating by sending rst
any character to the CPU and give then new
instructions on a new command line.

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

ARN [0..30] Autorange mode command.

In autorange mode, the absolute value of each

A/D conversion result is compared against

two limits:

• If lower than 1800 (out of 19999), range is
changed downwards, provided that it is not
already 2Ω.

• If the reading is higher than 19900, the range
is changed upwards, provided that it is not
already 2MΩ.

• If the argument in ADCn or RESn is greater
than 1 (average of many conversions), the
rst encountered overloaded or underranged
conversion causes an autoranging operation,
and after a delay, averaging is started from the
beginning. This guarantees a correct average.

The ICL7135 ADC circuit is overloaded, if
reading exceeds 19999. Then the AVS-47B
front panel display shows blinking zeros and
an internal overload indicator blinks between
true and false. During overload, a measure­ment like ADC;ADC? returns an exact zero,
which cannot be distinguished from a real
exact zero.

Because of this uncertainty, the AVS47­Serial/USB repeats once any conversion that
returned zero, which enables detection of
overload. The overload indicator is set to 1
(queried by OVR?).

ARN 0 means manual ranging. Argument
higher than 0 enables autoranging. A value
between 1 and 30 determines, in seconds, how
long the system waits after having changed

the range until a new autorange operation can

take place or until any new command can be
performed. A time like 5 seconds may sufce
at high excitations, when the bridge settles
quickly. A longer time, up to 15-20 seconds,
should be used at the lowest excitation in or­der to guarantee good balance before readings
are taken.

If the resistance changes several
decades, which is typical when switching
channel, the settling delay time of x seconds
is applied after each change of range. This
can make scanning unnecessarily slow or too
fast for good settling, but you can avoid it

OTHER COMMANDS AND QUERIES

OPC? Operation complete query

This query can be placed after slow opera­tions, like long averaging. When encountered,
it places a “1” into the output queue. It should
be the last item on a command row.

DLY [0..30] Delay command

The argument is delay time in seconds. Use
DLY for giving the AVS-47B time to settle
after a change in channel, range or excitation.

Note that autorange has its own settling delay
after each change of range before starting to
make A/D conversions. This delay is deter­mined by n in ARNn (see ARN).

SCK[1..10] This “sign-check” function is an alter-

native to the xed DLY delay. It is useful after
a change in range or input channel. When

the command interpreter encounters SCKn,

the function starts to make A/D conversions
at maximum speed and form differences
between successive readings. This continues
until two successive differences have had op-

posite signs n times, or the function has found

n sets of 3 successive equal readings. Then the

function concludes that data is either within
the peak-to-peak noise or it has settled to

within display resolution. The function exits
and operation continues with the next com­mand, which is typically ADCn.

by using the SCK[1..10] command. Refer to
description of SCK.

Use the RAN? query if you want to check the
range that was possibly changed by ARN.

Autoranging is especially useful in scanning.
If you do not use autoranging, you MUST
check with OVR? whether the single conver­sion or the average contained overload.

NOTE: The AVS-47B’s hardware autorang-
ing must not be enabled when the bridge is
under remote control. This would cause a rival
condition.

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

makes one conversion, if there is no over­load. The result is not used. SCK5 expects
differences to change sign n=5 times, which
indicates a reasonably good settling. Finally
an average is taken and the result is asked.

If the sensor’s value exceeds the range or is
below underrange limit (1800 counts), au­toranging must act. ADC1 will then make so
many autoranging operations that are needed
for nding a correct range. Because settling
on a low excitation is very slow, a long au­toranging delay (like the suggested 30 sec­onds) is necessary. A too short delay can cause
oscillation between ranges and this condition

should be strictly avoided - one has to reboot

the CPU by disconnecting its power! Once a
correct range has been found, SCK5 checks
for nal settling.

The long autoranging delay slows down
scanning when autoranging is needed. As soon

as the preset ranges are correct again, which
is the normal situation, scanning is faster

because xed settling delays are replaced
by SCK. It takes only the required time, not
more.

RST Reset command

This command works only when the program
is idling, i.e.it is not extracting commands
from a previously received command line or
performing those commands. RST cannot be

used for stopping long averaging or any other
pending operation. In such a case, wait or

reboot the interface.

The RST command sets the AVS-47B into
a known safe state: input 200Ω, channel 0,

range 2M, excitation 3µV and display to
R (resistance). Response line terminator is
CRLF and command separator is semicolon.

The AVS-47B is left in local mode, which is

shown by the blanked REMOTE light.

RST works differently than initial power-on
start: both leave the bridge in local mode, but
start-up does no alter the previous local-mode
settings of the bridge whereas RST changes
settings to these “safe values”.

The SCK function cannot prevent the A/D
converter from being overloaded. In such
a case, the ADC outputs only zeros. SCK
behaves as if it had received three equal read­ings (zeros in this case) and exits without any
additional delay.

The described method does not work if the
data has a trend that is large enough to prevent
differences from changing their sign. If there
is such a trend, the function exits after a time­out of about 30 seconds.

The function is faster if n is small, but then the
data may not have settled properly. A large n
guarantees better settling but is slower.

Some examples on how SCK could be used:

RAN3;SCK4;RES10;RES?

MUX4;RAN5;EXC2;SCK5;RES10;RES?

SCK works nicely if the measured resistance
is within the selected range. In case of ADC
overload, SCK exits quickly and the succeed­ing A/D conversion yields a zero resistance.

This can be prevented by using autorange,
but autoranging does not solve the problem of
good settling. Scanning is a situation where
a good tradeoff between speed and settling
accuracy is difcult to nd. Following is just
an idea of how automatic scanning could be
programmed.

Autoranging is enabled by ARN30 or some
other long delay. After having measured a
scanned sensor, its range is asked by RAN?
and saved as a variable for this channel. The
command line could be

EXC1;MUXnew;RANnew;EXCnew;SCK1;
ADC1;SCK5;RESn;RES?

Explanation: EXC1 selects the lowest excita­tion for preventing unintentional heating of
the next sensor during switching. MUXnew
selects the new channel. RANnew is the
stored range that was previously good for this
sensor. EXCnew is the suitable excitation for
this sensor. All these come into effect imme­diately.

The bridge starts to slew toward the new
sensor’s value. SCK1 waits until the slewing
changes direction for the rst time. ADC1

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

COMMANDS FOR THE TS-530A TEM­PERATURE CONTROLLER

The TS-530A is a very old design, and it has
been discontinued. We offer now a low-cost

analog temperature controller option for the

AVS-48 bridge. However, the AVS47-Serial/

USB includes also commands for the TS-

530A. They are for customers, who already
own this controller. These commands have no
corresponding queries. The analog setpoint
voltage, the heater output voltage and the
heater current can be measured by the A/D
converter of the AVS-47B bridge (see the DIS
command and refer also to the TS-530A and
AVS-47B manuals).

The TS-530A must be connected to the
AVS-47B with the supplied 37-way ribbon
cable for data and with the supplied short
BNC-BNC coaxial cable for the analog output
from the bridge.

The TS-530A does not have a separate
“remote” mode. Neither can the front panel
settings be read remotely. This means that
one can -but should not- change the remotely
programmed PID settings by using the TS­530A front panel switches, and the rmware
has no way to detect it. If this appears to be a
problem, write your program so that the set­tings of the TS-530A are updated frequently.
Re-programming existing settings without
changing them will not disturb the analog con­trol circuitry in any way.

SPT [10..42000] Set point command

Set point is given as a long integer from 10 to

42000. One digit corresponds to 100µV and
the range is from 1mV to 4.2 Volts although
only voltages up to 2V are meaningful when
using 530 with the AVS-47B. The slow inte­grating D/A converter of the TS-530A is very
accurate and linear, but it does not go to exact
zero, therefore 1mV is the minimum. Argu­ments less than 10 are coerced to 10.

If you want to give the set point in resist­ance, you must scale and convert it yourself
to a long or unsigned integer suitable for this
converter. For example, SPT10000 produces

ERR? Error query

The AVS47-Serial/USB has limited error

reporting capability. Errors are not reported
automatically, they must be queried using the
ERR? query. Possible responses:

0: No error

command XXXyyy not recognized:

The letter part of a command has been mis­spelled or is non-existent

query XXX? not recognized: The

letter part of a query has been misspelled or is
non-existent.

argument in XXXyyy exceeds
maximum:
argument in XXXyyy less than
minimum:

Every command has upper and lower limits
for its argument. If the given argument is

outside these limits, it is coerced to the nearest

limit and an error message is available.

AL input line (No 4 black in -F
version) stays at 0:

This input line from the bridge to the CPU is
used for synchronising the operation so that
each A/D conversion is read only once. The
error message is for trouble-shooting in a case
where communication fails.

ADC overload: The input voltage to the
ADC has exceeded 1.9999 Volts, which is
equivalent to the upper limit of each resistance
measuring range.

timeout in SCK: The sign-checking

delay function has not found expected criteria.
Reasons can be abnormally slow settling or
a trend in data. The function will exit after
a timeout. Then this error message becomes
available.

Error messages from one command line are

chained. The messages are verbal instead
of being numerical codes because they are
intended to be only programming aids. The

application program should minimise the pos-

sibility of error situations.

Error register is cleared by ERR?

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AVS47-Serial/USB-W CONVERTER

POW [0..7] Heater power range command

Power ranges are calculated for a 100Ω heater.
If heater resistance is higher, output voltage
compliance (about 10V) will reduce the maxi­mum power. If heater resistance is lower, the
available output current (100mA) will reduce
the maximum possible output.

0: Heater output is disabled

1..7: 1μW-10μW-100μW...1W

The heater output stage has seven current
sensing resistors 10kΩ, 3.16kΩ, 1kΩ, 316Ω,
100Ω, 31.6Ω and 10Ω corresponding to heater
ranges 1μW..1W. One volt across a sensing
resistor means full output of the range. Based
on the above gures, you can calculate correct
ranges for heaters other than 100Ω. Similarly,
you can measure the output current using
DIS6 and calculate the heating power from

RH*I2.

a 1 Volt setpoint. If the AVS-47B measures
on range RAN (=1..7), calculate the set point

integer from set point resistance RS as follows:

SPT = RS / (10 ^ (RAN-1)) * 10000
where RS=setpoint in ohms

If desired set point is e.g. 110
ohms and range=200R, (RAN=3)

SPT = 110/(10^(3-1)) * 10000 =
11000

PRO [0..11] Proportional gain command

Gain increases in steps of ve decibels. Values

are very approximate.

0..14: 5-10-15-20...60dB
15: no gain. Input of the proportional ampli-

er is connected to ground.

ITC [0..15] Integrator time constant command.

Values are very approximate.
0: integrator is reset to zero. P and PD mode

control

1-10: 1-2-5-10-20..1000s. Higher number

means weaker integration

11: analog integrator is latched by leaving its

input open

12..15: integrator is reset to zero. Same as
ITC=0.

DTC [0..7] Derivator time constant command.

Values are very approximate.
0: No derivation. P and PI mode control.

1..7: 1-2-5-10-20-50-100s

Higher number means stronger derivation.
High proportional gain with strong deriva­tion leads easily to oscillation of the control
system.

BIA [0..5] Power bias command

Power bias can be used to reduce control error
in P and PD modes. It is not useful in PI or
PID modes.

0..5: 0-20-40-60-80-100% of maximum
heater power. The highest setting is suf­cient for maximum output on the selected

heater range when proportional input is

zero and integrator is reset.

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AVS47-Serial/USB-W CONVERTER

CABLE SPECIFICATIONS

The AVS47-Serial/USB comes with two cables,
Picobus Cable and Serial Cable. The 5 meter Pi­cobus cable connects the converter to the AVS-47B
and the 1.5 meter Serial cable connects the box to
the computer directly or via an USB-232 converter.
This Picobus cable is distinguished from the Picobus
cable that is supplied with the AVS-47B by its male
25- and 15 pin D-connectors. The resistance bridge
is supplied with a cable that has male and female 25­way D-connectors.

Picobus Cable (PB25P15P6W5M)

The male DB25P and male DA15P are connected
by a braided (shielded) cable with 6 conductors (e.g.
Tasker C6015). Length: 5 meters.

DB25P DA15P Description

1 - braid grounded only in DB25P

4 4 CP clock from box to bridge
5 5 DI data from bridge to box
6 6 AL alarm line from bridge to box
7 7 Isolated ground

20 15 DC data from box to bridge
9 9 Isolated +5V (referred to pin 7)
Other pins are unused.

Note that the shielding braid must remain isolated
from everything inside the 15-pin connector shell. A
100nF ceramic capacitor with shortest possible leads
connects the braid to the connector shell. The braid
is connected to the shell of the 25-way connector at
the AVS-47B end.

This arrangement prevents the cable from act-

ing as an antenna at high frequencies while not

providing a path for ground currents at the mains
frequency. Inside the AVS-47B, Picobus signals and
its power supply are galvanically isolated from the
bridge ground .

Serial Cable (RS9P9S7W1.5M)

The male DE9P and female DE9S are connected
by a braided 1:1 cable of 6 conductors (e.g. Tasker
C6015). Length: 1.5 meters.

DE9S
DE9P RS232 Description

1 - -

6 DSR AL for Picobus applications
2 RXD RS232 output box=>computer
7 RTS CP for Picobus applications

3 TXD RS232 input computer=>box

8 CTS DI for Picobus applications
4 DTR DC for Picobus applications

9 ­5 Computer ground = shielding braid

Shielding braid is connected, in addition to pins 5,

also to both connector shells.

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For Interfacing the AVS-47B with Computers

AVS47-Serial/USB-W CONVERTER

RE-PROGRAMMING THE AVS47-Serial/
USB-W

The rmware can be updated by reprogramming the
Arduino Mega2560 board. In order to do this, you

need

- a USB cable (type A/B)

- Arduino development software for Mega2560. This
can be downloaded from Arduino WEB site.

- The new rmware version. It is available from us.

1. Follow Arduino’s instructions to download

and install their programming environment
software.

2. Open the four screws holding the “front” pan-

el of the AVS47-Serial/USB, the panel with

the DA15 connector. There must be no cable
from this connector to the AVS-47B. Plug the
“A” type connector into the USB connector of
your computer and the “B” end into the “hid­den” USB connector inside the AVS47-Serial/
USB. The box will now start, because it gets
power from the USB.

3. Make on your hard disk a directory that has

the same name as the new rmware le,
but without extension, e.g. “avs47_serial_
usb_1r2” . Arduino saves source codes into
directories that have the same basename as the
source code le. It creates such directories au­tomatically, so it is best to create the directory
yourself in a place where you want it be.

4. Place the new version of the rmware (e.g.

“avs47_serial_usb_1r2.ino” in the new
directory (Arduino calls the source code a
“sketch”).

5. Start the Arduino environment. Under Tools,

select Arduino Mega2560 board type. Select
also the USB port that your computer has as­signed to the CPU box.

6. Under the File menu, navigate to the new

rmware version and open it into the environ­ment.

7. Under the Sketch menu, select UPLOAD. If

you do not get any error messages, updating
has been done in a few seconds. You can now
detach the USB cable, x the rear panel and
connect the 25/15 Picobus cable to the resist­ance bridge and the -12V power plug. Then
test the new rmware using an RS232 termi­nal program or your own software. Sugges­tion: start conversation always by issuing the
IDN? query.

Before we email an updated version to you, please
check and tell us your old rmware version so, that
we can send also the old version for backup.

AVS47-Serial/USB-W TROUBLE
SHOOTING IDEAS

If you have difculties in getting the AVS47-Serial/
USB-W protocol converter to work, you can try the
following trouble-shooting procedure. The problem
might not be found this way, but it at least gives us
valuable knowledge of where in the system the prob­lem probably is. For making these tests, you need a
hyperterminal program, or any other program that
allows you to send serial commands to the AVS47­Serial/USB-W and read the responses. Typically,
today’s computers have only USB ports and then
you need a USB-232 adapter between the computer
and the protocol converter box.

Communication between the bridge and the box
uses four signals, two from the box to the bridge and
two from the bridge to the box. They are

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AVS47-Serial/USB-W CONVERTER

AL: “alarm” line telling that an A/D conversion is

ready to be read from the bridge

DI: data bits from the bridge (“instrument”) to the

box

CP: clock pulses from the box to the bridge

DC: data bits from the box (seen as the “computer”

by the AVS) to the bridge.

The sent and received data bits are synchronized
to the clock. Communication between the box and
the bridge is based on our proprietary synchronous,
serial “Picobus” protocol. Although this communi­cation is serial, it is NOT RS232. Please do not mix
synchronous and asynchronous serial formats. In
synchronous Picobus communication, a 48 bits long
string contains the complete state of the bridge,
which is sent in every transaction. While sending
the string, the CPU reads a response from the bridge
using the same clock pulses for synchronisation. The
response contains the state of the bridge just before
the transaction. Asynchronous serial communication

between the CPU box and the computer, on the other
hand, uses short mnemonic commands for control-

ling individual bridge settings and queries for read-
ing conversion results and settings that are currently
in effect.

The expression “protocol converter” means that
the complicated synchronous protocol of the bridge
is programmatically turned to understandable com­mands and arguments which are sent and received in
serial format that uses the legacy RS232 hardware
standard. Because of the slow speed of the AVS-47B
and tiny amounts of data, the simplest possible pro­tocol can be used (9600 bauds, 8 data bits, no parity
and one stop bit. No handshaking). It is based on
signals called TxD, RxD and ground. TxD transfers
data from the external computer to the box, and RxD
from the box back to the computer.

Signal lines between the CPU box and the com­puter are not galvanically isolated, whereas commu­nication between the CPU and the bridge is optically
isolated.

PROCEDURE

1) Remove the four cross-head screws that hold the

rear panel of the box (the panel with the 15-way

connector). Then pull of the top cover lid. If it

will not come, loosen also two topmost screws on

the opposite side. Place the box, so that the rear

panel is to the left. You can see a row of several
green and two red LEDs. They are for trouble
shooting. LEDs on the left (“bridge side”) show
signals to an from the primary interface of the
AVS-47B. They are marked with AL, DI, CP and
DC. At right are the two asynchronous signals,
TxD and RxD. The DI, AL, CP and DC signals
on the right have no meaning in this AVS47-Seri­al/USB-W application.

2) Connect the serial cable (RS9P9S7W1.5M) from
the box to the USB-232 converter or to your
computer, if it has a physical COM: port (RS232
port). Do not yet connect the cable to the resist­ance bridge.

3) Connect the +12V DC power plug. The green
“ON” light and one yellow LED on the Arduino
board should turn on. All trouble-shooting LEDs
(except possibly TxD, CP or DC on the right)
should be off.

4) Send command RST (“reset”) from the computer.
You should see very short activity of the TxD
LED. It is not dependent on the Arduino board.
If you do not see any activity although power is
ON, your computer program may be congured
wrong, or the cable is not in condition. If you are

not using our original cable, please check that
it is wired 1:1. Pins 2 of both connectors must

have been connected together, and also pins 3.
Pins number 5 are ground. (The so-called “null
modem cable” has cross-connected pins 2 and 3.
It is not suitable, because the cross-connection is
made inside the CPU box).

5) Send command IDN?. This should return
“PICOWATT,AVS47-SERIAL/USB,0,1R3” (or
a later revision). You should now see activity
also at the RxD light. The rmware program has
started succesfully. Much of the Arduino board
seems to be in order.

6) Send command RTS1. The green CP light on the
left “bridge side” turns on.

7) Send command DTR1. The DC light should turn
on. If this and 6) work, the CPU can send data
to the bridge.

8) Send commands CTS? and DSR? in turn. Both
queries should return 0 to the computer. These
signals have not yet been asserted by the bridge.

LabView is a trade mark of National Instruments, USA.

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AVS47-Serial/USB-W CONVERTER

9) Using a short piece of wire, connect pin 4 to
adjacent pin 5 in upper row of the 15-way con­nector. The pins are counted 1..8 from top right
to left and then 9..15 from low right to left. The
“DI“ LED should turn on and query CTS? from
the computer should return 1. Data can be re­ceived from CPU to computer.

10) Move the wire between pins 4 and 6. The “AL”
LED should turn on and query DSR? should
return 1. The Alarm signal can be received.

11) Remove the piece of wire. Send the RST com­mand again and the lighted LEDs should go off.

12) With the AVS-47B off, connect it to the box
using the 25-to-15 pin cable (PB25P15P6W5M).
Turn on the bridge. The “AL” LED should light.

If this did not happen, the problem may be in
the cable or optoisolator ISO204 (AL) in the
bridge. Set the bridge manually for CAL, 200Ω
range, 3mV excitation and R display.

13) Send command REM1. This should set the
bridge in remote mode, shown by the yellow
REMOTE led on the front panel. The bridge state
should have remained unchanged.

If the bridge remained in local mode, the
problem may be in the cable or in optoisolators
ISO201 or ISO202 in the bridge. The cable speci­cation is elsewhere in this manual.

14) Send command RAN4. The range should ad­vance from 200Ω to 2kΩ. There should be no
problems with this command, if the previous ones
have worked. This veries that bridge settings
can be remotely controlled. You may also want to
test commands MUX, EXC and DIS.

15) Send command ADC10. Ten A/D conversions
are made at 0.4 second intervals. All four LEDs
on the bridge section should show activity. The
rmware resets the AL signal and then waits max

0.4 seconds until the next conversion turns AL
on. A reading is taken and AL is reset again. The
cycle repeats 10 times. Query ADC? returns the
average of the 10 conversions.

If the response is zero or something strange, or

if the DI led does not blink, optoisolator ISO203
in the bridge may be defective.

RV-Elektroniikka Oy Picowatt
Veromiehentie 14
FI-01510 VANTAA

Finland

e-mail: reijo.voutilainen@picowatt.
WEB: www.picowatt.

If all these tests ended up succesfully, your problem
may be in the application program.

If the test stops to a failure, please let us know

your results so that we can try to help.

DECLARATION OF CONFORMITY

Manufacturer: RV-Elektroniikka Oy Picowatt

Address: Veromiehentie 14
01510 VANTAA

Finland

Telephone: [phone]
E-Mail: reijo.voutilainen@picowatt.

declares that under our sole responsibility

Product Name: AVS47-Serial/USB-W Converter

Product Description: Protocol Converter between the Picobus Primary interface of the
AVS-47B Resistance Bridge and RS232 or USB port of an external
computer.

is in conformity with the following Directives:

2004/108/EC: Electromagnetic Compatibility
2011/65/EU: ROHS Directive

and that the following harmonized standards have been applied:

EN 50 081-1: Generic emission standard, Part 1: Residential, commercial and
light industry

EN 50 082-1: Generic immunity standard, Part 1: Residential, commercial and
light industry

EN 50 581: ROHS

Additional information: This product uses +12V power from an external
mains adapter.

Vantaa, 14 March 2016 RV-Elektroniikka Oy Picowatt

Reijo Voutilainen

President

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AVS47-Serial/USB-W CONVERTER

INDEX

A

ADC 12
A/D conversion command 12
AL 18
AL? 10
Alarm line query 10
AL Picobus signal line 10

Arduino 5
Arduino Mega2560 5, 19
Argument part 7
Asynchronous 5
Autorange mode 13
Autoranging 14
Autoranging, hardware 14
AVS47-232 4
AVS47-IB 4
AVS-48 Resistance Bridge 16

B

Background 4
BIA 17
Bias power command 17
Blinking zero 12
Blinking zeros 14

C

Cable specications 18
Carriage return character 9
Case sensitivity of commands 7

Command delimiter 7

Command delimiter cmd. 10

Command line 7
Command part 7
Command separator 7
Comma-separated format 10
CP 18
CTS 18
Current sensing resistors 17

D

DC 18
D-connectors 18
Delay command 14
Delimiter 7
Derivator time constant cmd. 17
Deviation 11
DI 18
DIFFERENCE output 11
Directory 19
DIS 11

Disable heater output 17
Display selector cmd. 11
DLY 10, 14
DSR 18
DTC 17
DTR 18

E

Environment, Arduino 19
ERR error query 16
Excitation command 11
Excitation voltage 12
Exponential format 7

G

GPIB-Picobus 4

H

Hardware version query 10
Heater current of TS-530A 12
Heater power range cmd. 17
Heater resistance 17
Heater voltage of TS-530A 12
HW? 10
Hyperterminal 7

I

Identication query 10
Idle 15
IDN? 10
IEE-488.2 10

INP 10
Input selector command 10

Integrator time constant cmd. 17
Isolation, galvanic 4
ITC 17

J

Jumper JP203, AVS-47B 9

L

LabView 4, 9
LIM 10

Line terminator 6, 7
Line terminator command 10
Linux computer 4
Local 15

M

Mac computer 4
MAG 11
Magnier query 11

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AVS47-Serial/USB-W CONVERTER

Maximum number of characters 7
MAX? maximum query 13
MIN? minimum query 13
Multiplexer channel cmd. 10
MUX 10

N

Newline character 9
NULDEV 11

O

OPC 14
Operation complete query 14
Oscillation between ranges 15
Overload 14
Overrange 12
Overrange query 13

OVL 13
OVR 12, 13, 14

P

Picobus 4
Picobus cable 18
Picobus communication 4
POL 12
Polarity query 12
POW 17
Power bias command 17

Power-on start 15
PRO 17
Proportional gain command 17
Protocol converter 4

Q

QRATIO? “quality ratio” query 13
Query 7

R

RAN 10
Range command 10

Rebooting 15

REF 11
Reference command 11

REF POT / REF MEM 11
REM 10

Remote mode 15
Remote mode command 10
REPEAT command 13
RES 11, 12

Resetting the box 6
Resistance measurement cmd. 12

Response headers 7
Responses 7

Revision history 25
RFS 11
RS232 format 5, 6
RST reset command 6, 15
RTS 18

RXD 18

S

Safe state 15
Scanning 4, 15

SCK sign-checking delay 14
Send/Receive Serial 9
Serial cable 18

Serial format 9
Set point command 16

Set point of TS-530A 11
set point voltage of TS-530A 12

SET REF switch 11
Settling time 10, 14
Short circuit pieces 5
Sketch 19
SPT 12, 16

STD? standard deviation query 13
Synchronous 5

T

TER 7, 9, 10
Trouble shooting 19
TS-530A 11, 16
TXD 18

U

Underrange 14
USB-232 converter 5, 6
USB-232 Converter 4, 18
USB cable 19
USB connector 19
USB-Picobus 4

V

Voltage levels 5

W

Warranty 3

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AVS47-Serial/USB-W CONVERTER

REVISION HISTORY

1R0 => 1R1 2016-07-15

New DTR and RTS commands

New DSR? and CTS? queries

Timeout if AL is not set within 1 sec

1R1 => 1R2 2018-03-25

Correction in ADC function

New queries MIN?, MAX?, STD?, QRATIO?

Correction in operation of OVR query

Correction in operation of ERR? query

New sign checking delay function SCK

Multiple error messages are chained

1R2 => 1R3 2018-06-03

Added missing eld for serial number (=0) in
the IDN? response and removed spaces.

Both OVR? and OVL? can be used for check­ign overrange

Overrange of a single A/D conversion is
now decoded additionally into readings
ADC?=20001 and RES?=2000100.0000

Maximum length of the input string added
from 60 to 255 characters and length of a
command or query from 6 to 20 characters

Added new REPEAT command