Hello,

These are the datasheets for the sensors in question
LTS 25-NP: http://www.europowercomponents.com/media/uploads/lts25-np.pdf
TLI4970: https://www.infineon.com/dgdl/Infin...N.pdf?fileId=5546d4625607bd1301562c43e04f38ad

I'm not clear about the LTS 25-NP, it says a primary nominal current rms of 25 At. Also, a primary current, measuring range 0 +- 80 At. What's the real difference? I mean, I understand that it can measure up to 80A?.

The TLI4970 says it can measure up to 50A.

Which one would you recommend for measuring current on treadmills PMDC motors?

 

It seems to me that TLI4970 might be easier to process the data due to SPI interface. LEM transducer would probably need a opamp circuit. But LEM measure range is higher..

 

The peak that the LEM can handle is 80 ampere-turns (so 80 A for a single turn, where turns are counted by passes of the wire through the hole), but the maximum RMS current-turn product is only 25 At. This means that the allowable current depends on the waveform. For example, if the current were a rectangular waveform, the RMS current is the square root of the duty cycle multiplied by the peak current (e.g. at 40% duty cycle and 80 A peak the RMS current is 0.4^0.5 x 80 = 50.6 A). The bandwidth of the LEM module is high and the output is a voltage proportional to current, so it is suitable for analog control purposes. I haven't looked at LEM products for many years, but they used to produce a wide range of modules with ratings into the thousands of amps. They were not cheap!

The TLI4970 has lower bandwidth, and even to use the available bandwidth would require fairly high speed SPI. For something like keeping track of and limiting average motor current ramping up duty cycle at a moderate rate, it should be quite satisfactory. The programmable fast overcurrent output is a nice feature if you want to do cycle-by-cycle current limiting, which is very useful for protecting the FET or other switch. The package makes management of the current though it something of a challenge, and would require careful board layout and heavy copper (the test arrangement shown in the datasheet uses four layers of 0.105 mm (= 3 ounces per square foot per layer) copper connected together, which is lot of copper!). Reliably soldering that package to heavy copper would require a good reflow process (no more so than lots of other SMDs, but the pad design makes visual inspection virtually impossible).