Adret Electronique
_______________________________________________________________ Documentation in PDF format : Vol.1 Operation and maintenance manual (156 pages): (click the label below)
Vol2. - Part Lists (54p) -Schematics (45p) _______________________________________________________________ The Valhalla 2720GS is 25 years old. So, now, some problems of maintenance appear. ______________________ The NVRAM problem : this NVRAM is of type : Xicor X2221 It contains subroutines to start. It acts on the relays of release. We need a copy of this NVRAM to maintain the feature of our unit. Some others Xicor datasheet NVRAM : - X2201A - X2210 _____________________ The PAL EP320PC problem : this PAL contains all the soft of the 30 bits analog to digital converter. Unfortunately, it is protected to read with a security bit ! To insure the perpetuity of the unit, it would be desirable to make a copy of this PAL or to have the JEDEC file to program a GAL. Datasheet of the PAL Altera : EP320 : Selected devices to become obsolete : 1996 Lattice : PALtoGAL conversion : PaltoGal We search the soft WINPLACE... ____________________ The main microprocessor : it's a Motorola MC68A09 ____________________ For I/O : microprocessor Motorola MC6803 ____________________ Frequency counter : MC68A40 ____________________ Zener Reference module : NOVRAM XC2212 - datasheet Xicor 2212 : X2212 ____________________ The dual reference module is very impressive ! Here is the shematic : Reference Zeners These zeners are selected, aged and monitored for 9 to 12 months then statistically enhanced by the 2720GS multi-reference monitoring system. (Well, I would so like to know the secrets of this marvel!) ____________________ Valhalla's patent : May, 1978 ____________________ Others manuals Valhalla : - 2701C - 2701B - 2724A - 2500 - 2500EP - 2555A - 2575 - 2575A - 4100
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Valhalla 2720GS : Ultra-precision direct Voltage system
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The calibrator's calibrator...
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What is the Valhalla 2720GS ? The Valhalla 2720GS is the best voltage source never made to the world ! It's a very rare unit.
But what is the relationship with the french firm Adret Electronique ?
Well, but it's very simple : the principle of functioning is based on the Roger Charbonnier's patent of 1966, FR1484701A «Générateur étalon de tension continue ou de courant continu».
Roger Charbonnier was the french genius of the firm.
In 1987 Valhalla provided five first article 2720GS DC systems to the US Navy for compliance testing to MIL-T-2880C for EMI, RFI, accuracy, maintainability and 60 days of vibration failure analysis. Not only were all five units fully approved, but since 1987 Valhalla has shipped over 125 systems that the US Navy accepted for the MECCA II program.
The 2720GS delivers the performance required to calibrate the world's most accurate 7 1/2 and 8 1/2 digit DVM's yet does even more. It also contains an on-board autoranging digital nullmeter which permits the 2720GS to directly calibrate competition's best DC voltage calibrators. With this built-in Auto Null function, one touch is all that is required for the 2720GS to achieve a null with the DC source being calibrated. In the Auto-Null mode the 2720GS auxiliary read-out simultaneously displays the error of the unit under test (UUT) out to 0.01 PPM as well as the UUT's pass/fail status.
The 2720GS offers the best accuracy of any DC calibrator on the market. The temperature coefficient is the lowest of any DC Standard anywhere ! So low in fact, that the 1.6 ppm thirty days accuracy is specified for +/- 6°C from the calibration temperature !
The 2720GS has eight (yes, you read well...) internal highly stabilized reference zeners !
An internal real time clock and an ingenious on-board multi-reference monitoring system is utilized. This system's internal 30 bits A to D converter continually monitors each reference zener. Each reference module contains its own non-volatile memory wich stores calibration and drift rate data.
Direct Voltage output 10 nV to 1200V
The 2720GS direct voltage system displays its actual or standby output voltage down to 10 nV resolution or 0.01 ppm of full scale on all ranges. The extented resolution of the 2720GS is at least 10 times greater than that of the nearest competitive units. This resolution is made possible through the use of Valhalla's proprietary 32 bit pulse-width-modulated D to A converter technology.
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