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Cold Room & Temperature MonitoringEvery room's temperature and humidity on record — and a text the moment one crosses its limit

Modbus temperature and humidity sensors on one RS-485 line, the door and compressor contacts on digital inputs. The gateway logs every room on one clock, texts the duty manager when a room crosses its limit or a door opens, and keeps the record whole through any network drop.

  • Temperature + humidity
  • Door & compressor contacts
  • SMS on a crossing
  • Time-stamped record
  • Store & forward
Talk to our engineersWT400M 4G gateway
01

Watch it work

click a step to hold it
RS-485 · Modbus RTU · DI4G · MQTT + SMSRoom 1 sensorModbus · temp + RH−18.4 °C · 62% RH−18.2 °C · 63% RH−16.0 °C · rising−14.6 °C · HIGH−17.9 °C · 61% RHRoom 2 sensorModbus · temp + RH−19.1 °C · 58% RH−19.0 °C · 58% RHRoom 1 doorDigital inputClosedOpenCompressorRun contact · DIRunningMonitoring serverServer · MQTTDuty managerSMS · 4G modelsWiman gatewayLogger · triggersTrigger: door openTrigger: above −15 °CRS-485 · Modbus RTU · DI4G · MQTT + SMSRoom 1 sensorModbus · temp + RH−18.4 °C · 62% RH−18.2 °C · 63% RH−16.0 °C · rising−14.6 °C · HIGH−17.9 °C · 61% RHRoom 2 sensorModbus · temp + RH−19.1 °C · 58% RH−19.0 °C · 58% RHRoom 1 doorDigital inputClosedOpenCompressorRun contact · DIRunningMonitoring serverServer · MQTTDuty managerSMS · 4G modelsWiman gatewayLogger · triggersTrigger: door openTrigger: above −15 °C
  1. Step 1 of 5The gateway reads both rooms on the RS-485 line and sends the readings on the log interval, each with the gateway's time stamp.
  2. Step 2 of 5Room 1's door opens. A rule on the door contact fires once and texts the duty manager.
  3. Step 3 of 5With the door open, Room 1 warms. The readings keep logging; nothing else fires until the room reaches its limit.
  4. Step 4 of 5Room 1 rises above −15 °C. A trigger fires once on the crossing, texts the live value, and sends the room's readings to the server within a second.
  5. Step 5 of 5The door closes and the compressor pulls the room back down. The whole excursion is on the server, every reading with its time.
02

What connects to the gateway

EquipmentHow it connectsWhat the gateway reads
Temperature / humidity sensorRS-485 · Modbus RTUTemperature and relative humidity, one slave ID per room
4–20 mA temperature transmitterGateway input or WT36i cardA probe's temperature through its transmitter (the IO cards take 4–20 mA, not a bare RTD)
Door contactDigital inputOpen or closed — each change can raise an SMS
Compressor run contactDigital inputRunning or stopped, and run hours on the WT460M
Energy meter on the refrigeration panelRS-485 · Modbus RTUkWh and load, to see a compressor working harder than it should
03

What the gateway does here

Edge triggerA text the moment a room crosses its limitAbove a limit, below a limit, outside a band: each rule fires once when the condition comes true and texts up to five numbers with the live value and the time.
Door watchDoors left openA rule on the door contact texts when it opens — the commonest cause of a warm room.
Time stampsA record you can line upEvery room is read on the same clock, set from NTP, HTTP or the mobile network, so readings line up across rooms and sites.
Store & forwardNo hole in the recordReadings logged during a network drop go out oldest first, with their own time stamps, when the link returns.
Two serversYour system and your customer'sOn PRO and MAX the same readings can go to your monitoring server and to a customer's platform at once.
Supply watchKnow before the gateway goes quietThe gateway reads its own supply voltage, and a rule can text when the battery or supply feeding it runs low.
04

Which gateway fits

open a model for its full specification
PRO · 4GWT400MUp to 64 sensors on one line, triggers and SMS from its own SIM — no site network needed.View the WT400M →MAX · 4G + LANWT460MOn the warehouse LAN with 4G behind it, and texts either way.View the WT460M →PRO · EthernetWT600MOn the LAN with triggers and two servers; alerts go to your server (no SIM, so no SMS).View the WT600M →IO cardWT36iSix 4–20 mA inputs for transmitter-type temperature probes, on the gateway's RS-485 line.View the WT36i →
05

Being straight about it

The sensors set the accuracyThe gateway records what the sensors report. Calibration, and validation for a regulated record, belong to the sensors and to the system that keeps the record.
One text per crossingA rule fires once when the room crosses its limit, not again while it stays warm. A second rule at a higher limit can text again.
SMS needs the mobile networkTexts go from the gateway's own SIM on the 4G models; the network decides how quickly they arrive — usually seconds, sometimes minutes.
No bare RTDs on the cardsThe IO cards read 4–20 mA and 0–10 V. A PT100 probe needs a transmitter, or a Modbus temperature sensor instead.
06

Questions

Which temperature sensors work with the gateway?

Modbus RTU temperature and humidity sensors on the RS-485 line — one slave ID per sensor, up to 64 on the PRO and MAX series — and 4–20 mA temperature transmitters on the gateway's input or a WT36i card.

Will I get an SMS if a room gets too warm?

Yes, on the 4G PRO and MAX models (WT400M, WT460M). A trigger on the room's temperature texts up to five numbers when it crosses your limit, with the live value and the time in the message.

Will it keep texting while the room stays warm?

No. Each rule fires once per crossing. Add a second rule at a higher limit if you want a second warning, and a rule on the door contact to catch the usual cause early.

What happens to the readings if the network drops?

They are logged in the gateway and sent oldest first, with their original time stamps, when the link returns. The triggers keep running on the gateway meanwhile; the SMS itself needs mobile coverage.

Is the record good enough for an audit?

The gateway time-stamps and keeps every reading, so the record has no gaps. Whether it meets a particular audit depends on the sensors' calibration and on how your server stores the record.

How many rooms can one gateway watch?

Up to 64 Modbus sensors on the PRO and MAX series and 32 on the LITE series, on one RS-485 line. Large sites usually use one gateway per building.

RS-485 wiring guideHow a 4–20 mA loop worksHow store & forward worksWT36i analog card
Tell us the site, the equipment and the server.We will tell you which gateway fits, and configure it before it ships.
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