EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Fraser on October 07, 2017, 10:12:53 pm
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Global Specialties GS-3600 32CH 100MHz Logic Analyzer with LCD display
I own several Logic Analyzers that use a PC as the host and display. They all have pro's and con's. I fancied a logic analyzer that was self contained and included an LCD display, whilst having a reasonable weight and footprint on the bench. I already own several DSO's so an MSO was not considered in this case.
There are many elderly HP Logic Analyzers available relatively cheaply, but they tend to be rather large and heavy, plus they offer more capabilities than I honestly require. For this reason I chose not to buy an HP 'boat anchor'.
I stumbled upon a unit on eBay that I had not seen before and decided to take a risk on an 'unknown' that had moderate specification, but adequate for my humble needs. The unit is a Global Specialties GS-3600 32 Channel 100MHz Logic Analyzer that looks to have been built into a DSO case. (Nothing wrong with that though)
The specifications are as follows:
Input Channels: 32
Threshold Level: 6 individual adjustable threshold voltages: -6V to +6V - Resolution: 0.1V
Input Impedance: >100kOhms
Input protection: +-140V
Timing Sample: 1Hz to 100MHz (1S~10nS) Internal clock - Resolution: 10nS
Clock Sampling Channels: Internal, External 1 and 2
Sampling Signals: Internal code generator or External input
Storage depth 260K per channel
User Input/Output: Keyboard, RS232 and USB
The spec looked reasonable for the price being asked and I could find nothing similar close to its price, size and spec elsewhere. Added to this the advertised unit appeared to be in excellent condition BUT missing the input cables.
As veterans of HP and Tektronix Logic Analysers know, you should be VERY careful when considering the purchase of an incomplete unit, especially one that is without its input cable sets. These can cost as much as the base unit to buy and can be hard to find. With this in mind I started studying the design of the GS-3600 and its manual. I soon assessed the design as relatively simple in terms of its inputs. The way the manual described it, the input comprises the signal input grabber lead, a transition unit and a cable to the Comparators. That sounded very much like the comparators reside inside the main unit. The words 'transition unit' suggested a transition from Du-pont cables to a ribbon cable. I can now advise that I was correct in my thinking.
I bought the GS-3600 units for $89 each ! not a bad price for what you get. The units had previously been advertised at $149 which still isn't bad really. The lack of cables was likely scaring buyers away though. I think I got lucky. The GS-3600 retailed at $3000, yep, you read right $3000 !!! A tad over priced me thinks.
The first of the two units arrived this week and I eagerly investigated the front end design to see if I was correct about the location of the all important high speed comparators. The unit is in superb condition and I have identified the logic port connectors as standard 50 pin SCSI 2 types. That pleased me as it enables me to modify SCSI 2 COTS cables. I have already sourced some suitable cables and adapters for the task.
Upon opening the unit I found a lot of fresh air. There are two PCB's on the base plate, three on the front panel plate and a modular SMPSU on the base plate providing all required supply rails. Build quality is actually very nice and the casing metalwork and design is solid. On the input side, the GS-3600 uses 9 MAX901 high speed 8nS quad comparators. A MAX 529 8 parallel channel DAC provides the comparator reference voltages.
I will begin work adapting the SCSI 2 cables to form a selection of input cable options. That will need to wait until I have some spare time though. Another of these little units is currently en route to me so I will need to make two sets of cables.
The rear of the GS-3600 states that the unit is 120V 60Hz only. Interestingly, the small SMPSU module inside the unit clearly shows that it is a 220V capable unit. I investigated the SMPSU components and confirmed that it is indeed capable of handling 220V without concern. I tested the unit on UK power without incident.
Upon switching the unit on, it boots, self tests and then displays the default LA screen. This is split roughly 60/40 with 8 channels at the top and various data at the bottom. The display may also be set to a real data view. Upon boot, the LA activates its internal code generator and connects it to the input channels for display on the screen. This is what you will see in my pictures. The 5.7" 320 x 240 pixel LCD display is decent quality and crisp. The display may also be fed to a PC via the USB port if greater size or off-board analysis is desired.
The GS-3600 is available under other brand names as Global Specialties is just a re-badger and not an OEM. PeakTech in Germany sell the unit under their model number 1235. The OEM in China is called 'Da Hang Gong Si' and the date on the PCB's is 2005. Thankfully the user manual for the GS-3600 is available on the NET.
I will attach the GS-3600 brochure and the PeakTech user manual as that manual is small enough to fit on this forum. It also contains a block diagram. I also include some pictures of a complete GS-3600 kit including the data input cables and transition units.
Anyway, enough from me, lets get to some initial pictures of the unit and its internal parts......
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Brochure and PeakTech version manual
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My unit pictures start here......
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Display after boot etc.....
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Internal views.....
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Internal pics continued.... Front panel PCB's
Sorry that the cables are in the way on some pictures. The cable connectors have been professionally locked into their sockets using proper connector locking adhesive. Not hot melt glue as usually found !
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Internal pics continued....
The main processor and input PCB's
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Internal pics continued....
The SMPSU module
This is built 'in-house' by Da Hang Gong Si and is not a 3rd party bought in part.
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As can be seen from the pictures, this unit may not have amazing spec, but someone seems to have taken some care in manufacturing it.
Yes they have utilised a Digital Oscilloscope case, but the metal chassis is nice and solid and the plastic of good quality. The cables are all secured at their connectors using appropriate connector adhesive and the cables are provided with protection where appropriate. Note the black tubing over over the long ribbon cable and the use of spiral wrap on the single equipment hook-up wires to gather them together neatly. There is plenty of screw locking lacquer evident in the chassis and the safety earthing is fine.
All in all, I am very pleasantly surprised by what I found inside the GS-3600. It is no Hewlett Packard, but then I did not expect it to be, and it cost me less than my ZeroPlus Logic Cube units that require a PC to operate.
One glaring omission however...... There are no, repeat no, protocol decoders in the GS-3600 :o . I expected at least RS232, SPI and I2C, but no, nothing :( This was a surprise in a unit that originally retailed at $3000. Thankfully, if i need that capability, I can break out the Logic Cube or one of my other la's with protocol decoding built in. It would have been nice to have the basic decoders in the GS-3600 though. Oh well, for $89 I am not going to complain ;D
I previously asked on this forum if anyone else owned a GS-3600. Nil response to that request suggests that I am the only owner of these units here. There are others available on ebay USA for around the $150 mark. New Peak Tech branded versions sell for around 2000 Euros !
Fraser
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Is this made by Rigol or by GW Instek??
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I'm surprised they went for such a labour intensive construction. Either way you can buy used Tektronix and Agilent logic analysers for peanuts nowadays.
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nctnico,
As I detailed in my commentary, I considered the 'Boat Anchor' type offerings from HP and Tektronix. There are very good reasons for them being available for peanuts these days..... they are old, large and heavy. In some cases also overly complex for the task at hand. I have no doubt that they are very capable units, but boy are they hard to accommodate ! There is also the issue of reliability as some of the units are coming to the end of their operational lives and need some TLC to keep them running.
This may explain why people put up with less than ideal specs on many USB Logic Analyzers. Some are only 24Mhz clocked !
There does seem to be a bit of a void between the venerable, but bulky, HP and Tektronix offerings of yesteryear and the compact USB based LA's that are plentiful these days. If you want an LA with its own display and with the footprint of a modern DSO, you likely have to look at MSO's. The GS-3600 was very likely intended to fill that gap, but at an unrealistic price IMHO.
Global Specialties seem to specialise in supplying to the education market so the GS-3600 may have been intended for educational institutions? Education related kit always seems to suffer from inflated prices sadly.
Your point is well taken though. The boat anchors are cheap these days, the market has made them so with low interest and demand.
Fraser
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Hydrawerk,
It is built in China by Da Hang Gong Si and is then badged for whoever wants to sell it under their name. The case looks familiar and may be the same used for DSO's sold by say GWInstek, Owan or ATTEN ? The unit design is from 2005 so the DSO casing is larger than those that you see now. The case front panel even has the openings for the BNC connectors :) They are covered by the label around the input ports.
These days it can be hard to work out who actually manufactures the units as they often have no ID on the PCB's. In this case, the OEM is clearly marked on the PCB's. Sadly I cannot track down that OEM. They may not have a public presence on the internet.
Fraser
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Interestingly, regarding the supply voltage of the unit, as marked on the rear panel, the EU model from Global Specialties carries a 100-240V marking. My units came from the USA and are obviously intended only to be sold in 120V countries. Why not ship them all with the wide supply range marking ? Market protection maybe so people see the cheaper (?) US versions are 120V and think they cannot use them in 220V countries ?
Fraser
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Minor correction .....
Whilst the safety earthing regime presently in the unit passes a PAT physical test. I am not happy to see the rear panel to chassis screws used as part of the Earth path to the SMPSU module. I will fit a direct earth cable between the mains input connector earth bond point and the SMPSU earth bond point. The front panel earth bonding will also be investigated.
Fraser