Prototype of DAQ for commercial stand-alone devices with Ethernet interface
Sergey Trusov, Sergey Mikirtytchiants, Leonid Eltcov, and Yury Valdau
In the experiments at an accelerator it is often necessary to
continuously control some parameter of the installation with
high precision. It is very convenient to use for this purpose
commercial stand-alone measurement devices available on
the market. Often, in such applications there is no need for
the permanent control over all the device parameters, which
is usually available at the device front panel or via the web
interface. Hence, such equipment is usually configured at the
beginning of operation and perform a measurement either on
a command from operator at remote host or as a reaction on
the external trigger.
Nowadays, almost all the companies which produce test
and measurement equipment offer software solutions for the
readout and remote control of their devices. Unfortunately, in
most cases, solutions from different producers are not compatible with each other. The National Instruments [1] (NI) is,
essentially, the only company which offer hardware and software for almost all the commercially available devices on the
market. But LabVIEW software and hardware from the NI is
rather expensive and often exceeds the needs of a particular
experiment.
Recently, large international consortium of test and measurement equipment producers have started to develop and implement in to their products a support for the common opened
LXI standard [2] (LAN Extension for Instrumentation). It has
many important features, in particular, it uses industrial Ethernet interface for communication and affords a possibility to
supply a common trigger signal to the different devices. Unfortunately, many devices support LXI standard only to the
very limited extend and hence the major advantages of the
standard can not be used in the DAQ with these instruments.
Nevertheless, most of the modern devices have Ethernet interface and support telnet communications over TCP/IP protocol. Hence, it is possible to unify a readout of such equipment in one DAQ using standard industrial Ethernet. Devices
with serial or GPIB interfaces can be implemented into this
system by using commercially available Serial to Ethernet or
GPIB to Ethernet converters [3]. In such a system, synchronisation and triggering can be done either over the network
using a server which is running on the readout PC (software
trigger), or using a dedicated triggering scheme (hardware
trigger) which is connected to the device. A scheme of this
kind of DAQ for the TRIC experiment [4] is shown in Fig. 1.
The purpose of this system is to readout, calibrate, and control a Fast Current Transformer (FCT) [5] - the new sensor for
the bunched beam, using commercially available high precision measurement devices. A set of front-end electronics
located close to the FCT (shown in green) transmit a signal over the coaxial lines to the measurement devices (shown
in blue). The temperature sensors on a 1-wire bus are readout using a serial-to-Ethernet adapter [3]. Dedicated calibration scheme together with an arbitrary wave form generator
is used for calibration of the FCT readout scheme both in the
laboratory and at COSY.
Measurement devices from different vendors (Agilent,
Keythley, and Stanford Research) are readout, and controlled
over the Ethernet using server, written in C. The new Ethernet base device can be implemented relatively easily into the
DAQ readout using only one configuration file and dedicated
Fig. 1: Prototype of the DAQ for the TRIC experiment. The
Fast Current Transformer (in yellow) is readout and
calibrated using custom build front-end electronics
(in green) and commercially available stand-alone devices (in blue), which are triggered and synchronised
using dedicated triggering scheme (in violet), which
gets external control signals from COSY and other
experimental installations. All the devices are configured and readout over Ethernet (in red) by a server
running on one of the PC connected to this network
segment.
readout function. Experimental data from all the devices together with the corresponding time-stamp information from
every system are stored in a text or binary file on a readout PC running under the Debian Linux OS. The data stream
from the FCT readout system can be easily included into the
data stream from the standard DAQ from ZEA, usually used
for other experiments at COSY.
External synchronisation and hardware triggering for the
TRIC experiment is done by using the functionality from the
most advanced LXI device available in our system (Keithley
2601A) and the dedicated FPGA-based trigger module. The
trigger module gets control signals from COSY and other experimental installations and produces a hardware trigger signal. Devices get trigger signals and perform measurements
(or other actions) according to preloaded during initialisation
procedures.
The first tests in the laboratory have shown that this FCT
readout scheme allows one to reach the precision in averaged beam current measurement better than 10−4 for 1 mA
using the available lock-in amplifier. The FCT readout system together with a trigger scheme, which is under preparation now, will be used for the beam current measurement
during the TRIC beam time scheduled for summer 2016.
References:
[1] http://www.ni.com/labview/d/
[2] http://www.lxistandard.org/Default.aspx
[3] Perle Systems Limited, IOLAN SDS/SCS/STS/MDC
Users Guide, Ver. 4.1, 2014.
[4] Yury Valdau, Dieter Eversheim and Bernd Lorentz,
CBAC proposal E006, 2015.
[5] Bergoz Instrumentation, User Manual Fast Current
Transformer, Rev. 3.1, 2015.