Lesman Tech Tips

We’ve gotten feedback from several people who have asked what I carry around to deal with serial or Ethernet communications issues.  So I dumped out my comm tool bag and here’s the list of all the stuff.

HART communications requires at least 250 ohms so I carry my 250 ohm resistor with alligator clips on both ends for inserting into a HART loop.   I still use a serial HART modem because my current laptop has a native serial COM port, but some day I’ll have to switch to a USB or Bluetooth HART modem.

For checking out RS-232 and RS-485 comm connections, I carry
– a USB/RS-232converter (FTDI chipset)
– a USB/RS/485 converter
– a RS-232/isolated RS-485 converter
– a port powered RS-232/485 converter with a wall wart power supply
– a serial loopback test adapters, both male and female
– a couple straight through DB9F/DB9M extension cables
– a couple straight through DB9M/DB9M cables
– a DB9 Null modem adapter
– a couple null modem DB9F/DB9M cables
– a couple null modem DB9M/DB9M cables
– an RS-485 isolator/repeater
– male and female DB9 gender changers
– an RS-232 breakout box
– 120 ohm termination resistors
– a couple RJ11/12 cables (telephone cable)

For Ethernet, I’ll take along an unmanaged consumer grade ethernet switch, a cross over cable, a handful of straight CAT 5 cables of various lengths, a LAN/CAT cable checker, and a set of Paladin RJ-45 connector installation tools (punch, crimper), the ones with the orange handles.   There’s a pocket guide with illustrations of straight through and crossover connector wiring.

There’s the old trusties: a DVM for continuity checks, a collection of  jumper wires, wire strippers, long nose pliers and those tiny hollow ground screwdrivers that fit industrial terminal blocks. 

On rare occasions I’ll drag along a digital storage oscilloscope if I suspect excessive noise.

Just as important as the hardware is the software: known working installations of whatever software is involved and communications apps like Portmon to monitor serial ports, Process Explorer that finds serial ports, WireShark, terminal programs, Mactek’s Viator Check utility that proves a point-to-point HART connection and a collection of OPC servers and generic Modbus masters.  I’m not developer, I’m just trying to make stuff work that is already supposed to work, so I don’t have a high end serial analyzer that developers use.

If you’re into this stuff, you might be able to match the photos with the descriptions, like that Weekly Reader quiz from your youth.