The module in practice
The TM3DI8 is an 8-channel discrete input module in the Modicon TM3 family, accepting 24 V DC signals from sensors, pushbuttons, or limit switches. Each channel can be wired as sink or source, which means it handles both NPN and PNP outputs without extra hardware. That’s a real advantage when you’re consolidating different sensor types onto one backplane. Input impedance is 3.4 kOhm, drawing 7 mA per channel at 24 V. That’s within the typical range for IEC 61131-2 Type 1 inputs, so it will reliably see a signal from most industrial sensors. The guaranteed ON threshold is 15 V at 2.5 mA; OFF is below 5 V and 1 mA. Response time is 4 ms maximum for both turn-on and turn-off. The module is powered through the TM3 bus backplane – no separate supply needed. Typical consumption is 22 mA at 5 V DC, 5 mA on the bus. Isolation between channels and bus is 500 V AC.
It clips onto standard TH35-15 or TH35-7.5 DIN rail, or you can bolt it to a panel with the optional fixing kit. Physical footprint: 84.6 mm deep, 27.4 mm wide, 90 mm high. Rated for IP20, pollution degree 2. Operates from -10 to +55 °C horizontally, or -10 to +35 °C if mounted vertically. Humidity tolerance: 10–95 % non-condensing. Vibration resistance on DIN rail is 3.5 mm at 5–8.4 Hz and 3 gn at 8.4–150 Hz. Shock: 15 gn for 11 ms. Wiring uses an 11-pin removable screw terminal block, pitch 5.08 mm, accepting 0.2–2.5 mm² (AWG 24–14 solid). Maximum unshielded cable run from sensor to module is 30 meters for standard inputs.