Every PLC spec sheet says "0-10V analog inputs" and most buyers stop reading there. They should not. On the xLogic family the analog story runs deeper — PT100, PT1000, 0-20mA, 4-20mA, plus analog outputs in 0-10VDC and 0/4-20mA. That is a genuine temperture-and-instrumentation toolkit, not a token gesture.
Here is the part that surprises engineers who come from timer-and-relay backgrounds: a PT100 probe can be read directly. No external transmitter, no signal conditioner, no 24V loop supply. Wire the three wires, pick the input type in the software, and read degrees — the scaling happens inside the CPU.
Whichwich CPU Gives You What
The analog channel count varies by model, and this is where spec reading pays off:
- AI1-AI4 — PR-6, SR-12, PR-12, PR-12N, EXM-12
- AI1-AI6 — PR-14, PR-18, SR-22, PR-24
- AI1-AI8 — PR-18N
- AI1-AI8 plus AID-AIG — PR-26
Expansion modules add their own analog inputs — AI11-AI14 for expansion address 1, up to AI161-AI164 for address 16. A PR-26 with two analog Expansions covers a full instrument rack.
Real Case: Temperature Control on a Test Chamber
A plastics lab needed a temperature chamber held at 65 degrees plus or minus half a degree, with a datalog for the QC report. PT100 into a PR-18, PID block in xLogicSoft, heater driven by PWM, temperature logged via the free SCADA package over Ethernet.
Result: 0.4-degree stability and a QC archive nobody had to build by hand. Total analog engineering: one shielded cable and fifteen minutes of block wiring.
The 4-20mA Advantage Nobody Discusses
0-10V signals degrade over long cable runs — voltage drop is real, and noise couples in. 4-20mA is immune to series resistance and gives you a built-in wire-break detection: current drops to zero, which is outside the 4-20mA range, and a smart program can flag it as a fault. On pump stations and silo level monitoring, that single feature saves a service call every couple of years.
Use 4-20mA for anything farther than three meters. Your instruments will thank you, and your maintenance log will go quiet.
Wiring Discipline
PT100 is a low-level signal. It sits at the same voltage level as the noise in the cabinet. Shielded twisted pair, shield grounded at one end only, and keep it out of the same duct as contactor wiring. The manual's wiring section is short — it assumes you know this. If you do not, learn it before the first installation, not after the third mysterious temperature spike.
One more note: analog expansion modules are 12/24VDC only. There is no 220V analog module. Check the supply before you pop the module onto the rail.
Choosing the Signal Type Per Sensor
The sensor decides the input type, not the other way around. A PT100 probe wants its dedicated input — direct reading, no transmitter, no scaling in the field. A 4-20mA transmitter serves long runs and industrial noise. A 0-10V signal is fine for short, clean runs inside a cabinet. Match the signal to the distance and the environment, and half the analog problems in the industry disappear.
The generalist's rule: under three meters, any signal works; over three meters, prefer 4-20mA; for temperature with a probe available, use PT100/PT1000 directly. That one rule covers most plants. The exceptions — high-noise zones, very long runs, intrinsically safe areas — each have their own answers, but they start from the same question: what does the signal have to survive on the way to the input?
And verify the input type in the software before wiring the sensor. The CPU configuration for each analog channel — voltage or current, PT100 or PT1000, range — is a software choice, and wiring a 4-20mA transmitter to a channel configured for 0-10V produces readings that are plausible and wrong. Check the configuration at the same moment you tighten the terminal.
The Expansion Analog Modules: Read the Small Print
The expansion analog modules bring the same signal flexibility — up to six digital and four analog inputs — but they live by their own rules. They are 12/24VDC only; there is no AC analog module. Their addresses follow the expansion pattern (AI11-AI14 for slot 1, up to AI161-AI164 for slot 16), and their signals need the same wiring discipline as the CPU-side channels.
Plan the analog distribution before the module order. Which sensors land on the CPU's native analog inputs, which on the expansion module, and which on the bus via a remote device? That decision determines the addressing, the wiring runs, and the spare parts. A sheet of paper, ten minutes, and the panel design is done.
The pattern is the same everywhere in this platform: read the small print, match the module to the CPU family, and check the voltage before you clip it on the rail. The modules are forgiving. The people who skip the small print are the ones who remember why the manual exists.
The Cold-Junction Detail
Thermocouple users, this one is for you: the cold-junction reference is not a software checkbox, it is a wiring detail. The thermocouple wire connects to the input with the reference junction at the terminal — and if the terminal block runs hot, the reading runs hot with it. Mount the cold junction where the temperature is stable, keep the extension wire correct, and verify against a known probe before commissioning. Ten minutes of care beats a season of mysterious 3-degree errors.
Analog on a nano-PLC used to be a compromise. Here it is a feature. Use it.
