IRIS Instrumentation Committee
January, 2001

Site Visit - Refraction Technology

On January 17, Tom McEvilly, Bruce Beaudoin and Jim Fowler visited Refraction Technology to discuss their new generation data acquisition system (model DAS130). Two of these units were purchased by IRIS following the evaluation of DAS proposals late in 1999. Delivery is expected in summer, 2001. The following comments are based on the conversations we had and what we saw during the visit.

A prototype unit does not exist at the present time, but the major components have been breadboarded and tested, and a prototype of the case has been constructed. They are currently in the process of final board layout and construction of prototype boards. This process should be complete sometime in April or May. A prototype for IRIS should be available this summer. A major change from the design proposed in 1999 is the incorporation of the originally separate DSS (Disk SubSystem) into a new single-case design, where local storage and networking are with the digitizer function.

This unit represents an evolution of the current 72A instrument family. The basic operation and layout is similar, with a few exceptions. The major change is a new generation of electronics, lower power and better operating characteristics. Current PASSCAL data compression will be retained. A new digitizer chipset is used, scaled for +/- 10 v full scale and gains of 1 and 100. System noise levels around 2 counts rms are seen at X100 gain. Significant power savings are obtained by power cycling not only the GPS unit, but also the control processor. Total power consumption will depend upon the number of channels used and the sample rate. Normal operating ranges should have a power consumption of 0.7 to 1.0 watts.

The unit will have a commercial real-time operating system. The file system on the disk will be FAT32 so that it will be possible to plug the drives into almost any type of computer for direct access to the data. In order to speed development of the system and minimize integration problems with existing equipment, the command and control communications and data storage will use the same formats as current equipment. Additional commands may have to be added, but they will be done so that existing equipment will be able to ignore them.

The new unit features 5 circuit boards, hard mounted to the connector panel with no connecting cables. Movement of the boards with respect to the box should be minimal. The elimination of the card cage should make the system more rugged than the current system.

The box will have a built-in disk that can be swapped easily in the field. The unit will also support ethernet connections to the outside world utilizing either 10 base T or PPP. The unit will run the standard Ref Tek Protocol (RTP) that is used on the current 72A instrument when connected to a network.

The GPS receiver and antenna are an external unit, power-cycled with approximately 10% duty cycle. The clock will be able to obtain a lock much quicker than the current units and will need to stay on for tens of seconds thereafter. The internal oscillator frequency will be compared to the 1 pps signal from the clock and will be corrected to maintain correct time.

All boards in the system will have ID tags that will be read at power-up. These ID tags will store board serial number, revision level and other key information to allow tracking of components.

Site Visit - Quanterra/Kinemetrics

On January 30, Tom McEvilly, Shane Ingate and Jim Fowler visited Kinemetrics to discuss their new generation Quanterra data acquisition system (model Q330). Two of these units were purchased by IRIS following the evaluation of DAS proposals late in 1999. Delivery is expected in late spring, 2001 The following comments are based on the conversations we had and what we saw during the visit.

A full prototype instrument does not exist at the present time. The unit follows closely the designed proposed in 1999. Most of the boards have been prototyped, with the exception of the main controller. Work on this board is proceeding and should fit with the expected delivery time to IRIS. The main system controller on the Q330 is a DSP unit, rather than some sort of standard microprocessor. Controller power consumption is undetermined at this time, but should fall somewhere in the 100-500 mW range. Analog channels consume about 100 mW per channel. Because unused channels can be powered down, it is expected that the 'standard' instrument will feature 6 channels.

The GPS receiver board is internal to the unit. It will be able to run in either power-cycled or continuously. The basic GPS power is around 300 mW in continuous operation, including the active antenna.

The Q330 utilizes an A/D converter that was designed and constructed by Quanterra. In order to get the low power some noise performance was sacrificed compared to the current Quanterra units. However, the noise curves that were shown indicate that the unit exhibits excellent performance.

The basic unit communicates to the world via UDP/IP protocols. All command and control ports on the unit utilize SLP protocols. All local ports are configurable with respect to data speed. There is an IR port to use in communicating with a palm top computer. On-site storage or TCP/IP communications will be accomplished with a second piece of hardware called a "baler". There are several versions of balers envisioned for the system. These will be able to provide customized interfaces to the system. Hardware development for the baler is lagging behind that of the main unit. However, the functions of the baler have been simulated on several different computer platforms.

The Q330 has a series of LEDs to display the unit status while operating. All boards on the unit will utilize ID tags that will provide information on the configuration of the instrument automatically. If sensors use the chips, arrangements have been made to be able to read them also.

All of the software is stored in flash memory and there is a standard 8 MB of memory available for data so that the unit does not have to power the baler very often.

The Q3300 supports up to 4 connections at one time. In order to connect to the unit you must know the IP address, the serial number and have a password. The Q330 does not initiate connections. It waits for a service request from a remote control unit.

Control set-up and data formats are different from previous Quanterra units. The data come in 1 second packets in compressed format. All data time tags do not include the fir filter lag. Even though data come out every second, data from different sample rates will have different delays due to the fir filters.

The case is an aluminum extrusion with end caps screwed on. The main internal electronics package is in a second metal case that "floats" with respect to the front panel.

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IRIS Instrumentation Committee
May, 2001

DAS development. We are getting close to having initial prototypes for testing. In March Quanterra reported on successful testing of the Q330 analog circuitry and digital processor. All the boards had been built and tested in varying degrees by the end of march. We fully expect to be field testing the Q330 production prototypes this summer.

We will visit RefTek late in May to assess progress on our other new DAS. By the time of the Workshop in June, we should have a reasonably firm date for delivery of initial prototypes for field testing later in the summer.

Another DAS, from SAIC, has been presented to IRIS for consideration for use in the GSN, particularly in the IDA stations. The unit is under test at Samdia Lab (Dick Kromer), and the Instrumentation Committee wil be expected to evaluate the results and make a recommendation to the GSN Standing Committee on its suitability.

Sensor investigations. We have a test facility operating at Berkeley in the BKS vault, with a dedicated Q4120 8-channel DAS installed to allow recording of various sensors in the short-period, broadband and strong-motion categories. The sensors under test are colocated on the BKS pier with the continuously-running standard instruments for reference: STS-1, STS-2 and FBA-23. At this time we are testing the Kinemetrics Episensor, the RefTek 131-02, the new PMD unit, Endevco's model 86 and Wilcoxon models 731-B and 9XL We expect shortly to receive a low-noise MEMS unit for testing also, from Applied MEMS, Inc. (their digitally fedback unit. We hope to be able to report on progress at the Workshop. The goal of these comparisons is to be able to place the various sensors on a common basis in terms of sensitivity, bandwidth, fidelity and self noise, so that it will be clear where they might be appropriate selections in the broad range of applications covered in the EarthScope and ANSS plans, or in traditional IRIS programs.

We still hope to see the Chinese broadband sensors for testing in New Mexico, whenever USGS has a new vault facility. We have not heard from the French recently on their progress in commercializing the Mars seismometer for terrestrial use.

Communications. New satellite links are being tested in field deployments by PASSCAL.

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