36,230
edits
No edit summary |
(introduction year per TekScope 1976 V.8 N.4) |
||
(31 intermediate revisions by 4 users not shown) | |||
Line 1: | Line 1: | ||
{{TM500 | type=AM503 | mfg=Tektronix | function=current probe amplifier | class=amplifier | image=Am503_front.jpg | introduced=1976 | discontinued=(?) | manuals= | |||
* [http://w140.com/smb/AM503_SM.pdf Tektronix AM503 Manual (OCR, PDF)] | * [http://w140.com/smb/AM503_SM.pdf Tektronix AM503 Manual (OCR, PDF)] | ||
* [http://w140.com/am503a_service.pdf Tektronix AM503A Manual (PDF)] | * [http://w140.com/am503a_service.pdf Tektronix AM503A Manual (PDF)] (no schematics) | ||
* [http://hakanh.com/dl/docs/hardtofind/AM503A%20Schematics.pdf AM503A schematics] | |||
* [[Media:070-8766-05.pdf|Tektronix AM503B AM5030 Manual (PDF)]] | |||
}} | |||
Versions AM503A and AM503B have digital readout of deflection factor. | |||
The current probe input is an [[Amphenol 165-12 connector]]. It contains pins for hall element and transformer connections, lock detection, probe degaussing, and probe type encoding. | |||
{{BeginSpecs}} | |||
{{Spec | Bandwidth | | |||
* A6302: DC to 50 MHz | |||
* A6312: DC to 100 MHz | |||
* A6303: DC to 15 MHz | |||
* A6304XL: DC to 2 MHz | |||
}} | |||
{{Spec | Sensitivity | | |||
* A6302, A6302XL, A6312: 1 mA/Div to 5 A/Div | |||
* A6303, A6303XL: 10 mA/Div to 50 A/Div | |||
}} | |||
{{Spec | Range | | |||
* A6302: max. 20 A continuous, 50 A peak | |||
* A6303: max. 100 A continuous, 500 A peak | |||
* A6304XL: max. 500 A continuous, 700 A peak | |||
}} | |||
{{Spec | Scope output | 10 mV/Div}} | |||
{{Spec | Power | 17 W}} | |||
{{Spec | Compatible probes | | |||
* [[A6302]] (20/100 A, DC-50 MHz), [[A6302XL]] (20/100 A, DC-17 MHz) | |||
* [[A6312]] (20/100 A, DC-100 MHz) | |||
* [[A6303]] (100/500 A, DC-15 MHz), [[A6303XL]] (100/500 A, DC-10 MHz) | |||
* [[A6304XL]] (500/700 A, DC-2 MHz) | |||
* [[CT4]] with A6302, A6302XL or A6312 (2000/20000 A) | |||
}} | |||
{{EndSpecs}} | |||
===Rear interface=== | |||
The output can be detached from the front panel BNC socket which has a [[Peltola connector]] on the inside, and re-attached to a Peltola socket near the top of the interface connector, where it is terminated in 50 Ω and brought out on pin 28A (ground on 27A). | |||
==Background== | |||
Regarding the AM503, Dale Dorando says: | |||
<blockquote> | |||
The AM503 was a redesign of the [[P6042|6042]] current probe from 1967. | |||
It was initially going to be an oscilloscope plug-in. | |||
About 80% through the project design a new line of products was started called TM500. | |||
It was requested that we change the design to be a TM500 plug-in module instead. | |||
The AM503 front panel still looks like a scope’s plug-in. | |||
The AC/DC switch and 5 MHz bandwidth switch, for example, were left on the front panel from the oscilloscope design. | |||
There are still some remnants of the oscilloscope circuits, such as the [[cam switch]] that interfaced to a circuit board that sets the scope’s readout in amps/div. | |||
The square pin header connector on the back of the circuit board was for the readout, but not used. | |||
The high frequency amplifier was differential to accommodate an oscilloscope’s differential input. | |||
The last change was the output stage that was added to convert the differential circuit to single ended, and then output that to a front panel BNC. | |||
<br /> | |||
The AM503 was also intended to work with future higher frequency probes, like the [[P6022]] with an added hall device for DC measurements. | |||
The smaller P6022 had a 120 MHz bandwidth, whereas the [[P6302]] was only 50 MHz. | |||
The design engineer (actually only an R&D technician) moved to the TM500 engineering and evaluation group before this probe was created. | |||
The AM503 was being developed in the Accessories division in Beaverton, since that’s where the other current probes were designed. | |||
That was unusual as all the other plug-ins were being designed by the TM500 group on Walker Road, near Hillsboro. | |||
The AM503 was one of the first plug-ins for the TM500 line of products. | |||
It required more power than the current plug-in designs so the transformer and supply were changed in the TM500 frames early on just for the AM503. | |||
<br /> | |||
There were some innovations that were incorporated in this design: | |||
The [[cam switch]] with replaceable laser trimmed attenuator resistors, a 1 GHz Gilbert cell op amp (actually developed by Howard Jones in 1963). | |||
This IC, [[155-0078-xx]], was being developed by Tek’s IC department. | |||
(At the same time these IC designers were teaching the technology at the University of Portland as part of Tek’s excellent education and training program.) | |||
The [[Peltola connector]], developed by Tek’s Ron Peltola, a very low cost connector that worked well, even for the highest frequencies. | |||
A BNC was adapted to be used with the Peltola and is used on the front panel. | |||
<br /> | |||
A large section of the AM503 was basically duplicating the front end of an oscilloscope since that was the original design intent, | |||
so it was thought later that the differential amp section could be eliminated and the amplifier made much smaller and even become part of a standalone probe. | |||
A prototype was created (author’s senior project at the University of Portland) but shelved, as there was no longer an engineer in Accessories for current probes. | |||
Much later it gave rise to the TCP series of stand-alone current probes. | |||
<br /> | |||
The [[P6302]] and [[P6303]] probes utilized a Hall device that was manufactured in the clean room of the Accessories Manufacturing group. | |||
It was deposited onto a bar of ferrite that was later assembled into a U shape with other ferrite and potted in a mu-metal can along with the transformer bobbins. | |||
The Hall device used for the DC measurements used a vacuum deposition process with indium antimonide. | |||
The cores were lapped and polished to a few Fresnel lines flatness to minimize the gap on the sliding ferrite. | |||
The L/R time constant affects the point where the Hall device and coils’ bandwidths crossover. | |||
<br /> | |||
An interesting aspect of the design was trying to find a way to test and calibrate the peak current pulse on the larger P6303. | |||
Luckily we had the tube lab. We developed an argon filled thyratron that could discharge a 4 kV charge line into a 4 Ω load. | |||
The load resistor was designed and built by Tektronix. A large rectangular ceramic plate was coated with a metal film resistor. | |||
It had a voltage divider tap to allow for a safer measurement point. It was laser trimmed for accuracy. | |||
The current probe would measure the current to ground through this resistor, so the voltage was near zero for the user. | |||
The 4 kV supply was charged into a 4 Ω transmission line so a clean high current pulse would be generated. | |||
This concept was taken from Tek’s [[109]] pulse generator. | |||
<br /> | |||
A trigger circuit was designed to fire the grid. It was based on the xenon flash circuit of the [[C-5|C5 camera]] flash, also in the Accessories group. | |||
The first prototype I made arced across the laser trim lines in the metal film resistor as they were cut perpendicular to the current flow. | |||
This caused high voltage gradients across the film and thus the arcing across the cuts. | |||
We changed the laser trim to be parallel to the current path along the outside edges. | |||
That’s what was used in manufacturing for calibrating the risetime of the P6303. | |||
<br /> | |||
Also interesting, the P6303 required special potting epoxy developed by 3M. | |||
The epoxy used in other current probes put excessive stress on the larger ferrite that caused the inductance to drop to zero | |||
due to the magnetostriction property of ferrite. The epoxy could even also cause shear fractures in the ferrite. | |||
</blockquote> | |||
==Pictures== | |||
====AM503==== | |||
<gallery> | <gallery> | ||
Am503_front.jpg | AM503 front | |||
Am503_left.jpg | AM503 left side | |||
Am503_right.jpg | AM503 right side | |||
Tek am503.jpg | AM503 | |||
Tek am503 t1.jpg | AM503 | |||
Tek am503 t2.jpg | AM503 feeding a [[TDS744|TDS744A]] | |||
</gallery> | </gallery> | ||
====AM503A==== | |||
<gallery> | |||
Tek am503a.jpg| AM503A | |||
</gallery> | |||
====AM503B==== | |||
<gallery> | |||
Tek am503b.jpg | AM503B | |||
Tek am503b tm502a 1.jpg| Two AM503B in a [[TM502A]] | |||
Tek am503b rear.jpg | Rear view of two AM503B plug-ins | |||
</gallery> | |||
==See also== | |||
* [[AM5030]] | |||
* http://www.tek.com/datasheet/current-measurement-system-probes |