Main differences between HP 8116A and HP 8112A - Page 1
Forum section: electronics / testgear

author: pascal_sweden
author_rank: Super Contributor
timestamp: July 24, 2015, 11:03:43 pm
content: What are the main differences between HP 8116A and HP 8112A?Should I get the higher model? I read somewhere on an Ebay auction that the lower model is faster, but what do they mean with that?Do both models have a battery inside? Where is it positioned? Photos?

author: edavid
author_rank: Super Contributor
timestamp: July 24, 2015, 11:11:11 pm
content: HP 8112A is just a pulse generatorHP 8116A adds a function generatorDon't buy either one - repair nightmare

author: wn1fju
author_rank: Frequent Contributor
timestamp: July 24, 2015, 11:59:02 pm
content: There is also the HP 8111A which is the junior 20 MHz function generator to the 50 MHz HP 8116A. As indicated in the previous post, these can be problematic if you are buying blind (for instance, eBay) because they have HP proprietary chips that do much of the functionality. Unobtainable (except from another unit). Which is what happened to me when I bought a "broken" HP 8112A only to open it up and find all five of the hybrid chips gone! Anyway, I was luckier with the HP 8111A - that only had a short on one of the boards that stopped the power supply. My overall impression, at least with the 8111A, is that the specs are not particularly good, nor is there much accuracy between what is shown numerically on the display and what the actual output waveform's properties are.

author: Smith
author_rank: Frequent Contributor
timestamp: July 25, 2015, 07:09:06 am
content: Agreed, I have an 8116A and it isn't that good. It's basicly unable to be calibrated it to any accuracy without replacing all single turn pots for multi turn ones (approx 20 of them) besides the whole procedure is a nightmare. Some adjustments (symmetry related) should be done by replacing standard resistor values.Basic accuracy is bad and quite temperature dependant, and the fan is completely horrible (although I replaced mine with an more silent one).Besides that it will probably be too large to fit on most desks, as it is very deep.Still don't know why some cost a small fortune on ebay, if seen multiple ones for up over 2 grand. Thankfully mine was free, although defective. Took me quite some time to fix, as the problem was an option which wasn't mentioned in the main schematics.

author: dom0
author_rank: Super Contributor
timestamp: July 25, 2015, 08:46:16 am
content: These are basically analog function generators controlled by an entire PCB of DACs.They thus have the same precision and drift issues that all analog FGs have, although repeatability will be better / easier. Calibration is done by many, many pots buried in the unit and is complicated with a few interdependent adjustments. They contain a number of ASICs which often die from overtemperature and can cost as much as an entire unit.

author: Electro Fan
author_rank: Super Contributor
timestamp: July 25, 2015, 10:10:14 am
content: I think maybe after this thread the eBay prices might start drifting downward a bit

author: edavid
author_rank: Super Contributor
timestamp: July 25, 2015, 03:29:37 pm
content: Quote from: Electro Fan on July 25, 2015, 10:10:14 amI think the demand comes from industrial users who don't want to rewrite their automated test procedures.

author: dom0
author_rank: Super Contributor
timestamp: July 25, 2015, 03:32:28 pm
content: Yes I think that, too. There is even some company that sells generators with about the same specs and the claim they are 100 % 8112A compatible.edit:http://www.marvintest.com/Product.aspx?Model=GP1612H+Series

author: Electro Fan
author_rank: Super Contributor
timestamp: July 25, 2015, 06:07:11 pm
content: That is very interesting. It shows the powerful (technical and economic) relationship between software and test equipment and probably has implications for how test equipment and software might evolve, especially in an era of cloud computing and the Internet of Things/Everything (IOT/IOE). What if instead of test equipment accessing cloud applications, the Internet of Things (DUTs) accessed test equipment via the cloud. Due to the proprietary nature of R&D, desire for security, and technical issues such as network latency it might be that such a model wouldn't be practical for design work, but maybe for some monitoring, maintenance or educational applications.