Scales question

[Lo-Fi]

Hi Yuriy

I've been looking at Touch DRO for some time now, but a couple of things have made me hold off..

First and most importantly: scales. I'm in the UK, and found it almost impossible to find reasonably priced scales where suppliers give any info on what type they are, which makes it very tricky to figure out if I'm buying something compatible. Do you have any suggestions please?

Secondly the shipping cost. A small thing, but it's a large percentage of the purchase cost to ship it over here. This made me look at the arduino self build solution, but figuring out what scales are usable with that proved even harder.

I love the concept though, and really want to get myself a setup going on my Bridgeport! Any suggestions/advice would be most welcome

 

[ycroosh]

Hi,
At this point there are five types of "remote display" scales available on the market. All of them are supported but:
iGaging DigiMag, EZ-View and Absolute DRO are the only ones with Micro-USB cables (to my best knowledge) so, they are all supported by the TouchDRO Adapter for iGaging Scales
iGaging DigiMag with Mini-USB cables can be plugged into the same TouchDRO adapter using Mini-to-Micro adapter cable
Shahe "Remode Digital Readout with Square Display" come with Mini-B and can be used directly with the new TouchDRO adapter for Shahe scales
iGaging AbsoluteDRO Plus with Mini-USB cables are supported by the former, but need to use Mini-B breakout boards, since the pinout is different.
Shahe "Remote Digital Readout with Round Display" are supported, but since their cables are hard-wired into the head, they need to be cut and soldered to the TouchDRO board.
Most modern glass and magnetic scales (and 100% of Chinese DRO scales you can find on Ebay, AliExpress, etx.) use 5V quadrature output and are supported by the "Quadrature" TouchDRO adapter.
Other Chinese scales are generally supported by the Mixed Scale firmware, but need a voltage amplifier circuit.
I've been asked this questions quite a few times recently, so I will post more details on my site in a few day.

As far as shipping, I know that it's high, but this is what USPS charges me. I have two options - First Class Main International, which is around $14 and USPS Priority International, which is $35. I used to offer First Class option, but USPS was loosing around 15% of my packages, and another 10-15% were taking so long that people were starting disputes on PayPal. I don't have enough profit margin built into the boards to "eat" that cost, unfortunately.

On a related note, I'm resurrecting the DIY kit that will cost around $50 (USD) + shipping that is basically a kit version of the Shahe/iGaging adapter. I'm waiting for the shipment of BT modules that has been delayed by Chinese New Year and the Corona virus outbreak.
Hope this helps
Yuriy

 

[Lo-Fi]

Thanks, that makes it a little clearer

I've been looking at these:

JCXE encoder linear scale for digital readout DRO 150 to 600 mm UK stocking | eBay

Find many great new & used options and get the best deals for JCXE encoder linear scale for digital readout DRO 150 to 600 mm UK stocking at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

Which if I'm understanding correctly should work with the adaptor for glass and magnetic scales? The micro USB ones don't seem as accurate and they're not so easy to get hold of in larger sizes over here.

 

[ycroosh]

Ah, those are standard glass scales. They work great, but you want to make sure the seller can tell you the spinout. You often can't guess without an oscilloscope.
Regards
Yuriy

 

[Lo-Fi]

Pinout on the listing, so sound like I'm good to go.

I'll pop in an order shortly!

Thanks for the quick responses

 

[Bi11Hudson]

A quick question if I may:
I have been following the various discussions on DROs and what bothers me is the discussions on "glass" scaling. I am familiar with LVDT positional transmitters, having used them in the past.

The specific question I have is: where do LVDTs fit in the world of positional transmitters/transducers. I would assume a digital transducer of some sort but I'm not up to speed on what such a device would consist of.

Any pointers you can provide would be greatly appreciated. I will take the answers here or personal eMail, as you prefer.

Bill Hudson​

 

[ycroosh]

Bill,
I suspect inductive scales work on the LVDT (linear variable differential transformer), but they are insanely expensive, so I dont see them in use often. Magnetic and capacitive scales are similar, but instead of electromagnetic coupling they use magnetic and capacitive coupling.
Glass scales are basically linear optical encoders.
Regards
Yuriy

 

[Bi11Hudson]

I'm not so sure I understand the foo fah rah about these things. Especially if the difference is as you stated. Capacitive coupling would be essentially unstable in a shop environment. In a "gray room" or better, it might be controllable. But I don't see how it would be stable with humidity changes or oil and dirt on the sensor element.

The original question arose because I used LVDTs when I had "automated" my machines way back when. The ones I have are only about 4 inch stroke with 4-20 mA output. Salvage from an industrial user~~~ They were extremely repeatable but the electronics were a bear to tune initially. Scaling uA to thousandths took as much electronics as the LVDTs to measure.

The bottom line I suppose is the question of whether these contraptions are true digital devices or are they simply analogue devices with A/D converters on the display.

I think I need to apologise, my mind has drifted over the years and my memory is not what it once was.

.

 

[JFL4066]

Yuriy and others,

Has anyone shortened their armored cables on the magnetic or glass scale readers? Can you remove the DB9 connector and re-attach it?

 

[ycroosh]

Yes, fairly easily. I used a Dremel to cut it off and then trim the wires.