DS18B20-PAR | GUILCOR SENSORS

DS18B20-PAR
Temperature sensors

Parasitic-powered 1‑Wire sensor for easy installation and precise temperature monitoring in compact electronic systems.

Maximum precision
+/- 0.5°K

Minimum temperature
-55°C

Maximum temperature
+125°C

Minimum dimensions
4 x 6 x 27

Response time
Fast

Self-heating
Low

Price
Low

Drift
Low

What is a DS18B20-PAR sensor ?

The DS18B20-PAR (for Parasite Power) is a version of the DS18B20 optimized to operate without a dedicated power supply.

It only requires two wires:

one for the signal + power,
one for ground (GND).

It draws its energy directly from the DATA line of the 1-Wire bus, thanks to an internal capacitor.

Result: minimal wiring, ultra-low power consumption, and simplified integration into standalone systems.

Operating principle

The DS18B20-PAR converts the measured temperature into a 12-bit digital signal transmitted via the DATA line, while powering itself from that same line.

T = Raw Value / 16

During the conversion phase (up to 750 ms), the sensor consumes the energy stored in its internal capacitor, without external power supply.

Technical specifications

Parameter	Typical Value
Measurement range	−55 °C → +125 °C
Typical precision	±2,0 K (−10 → +85 °C)
Resolution	9 to 12 bits (configurable)
Conversion time	93,75 to 750 ms
Alimentation	Parasitic mode only (DATA + GND)
Interface	1-Wire Digital
Unique identifier	64 bits (family 0x28)
Annual drift	Low (±0.2 K/year)
Case	TO-92, waterproof IP68 cable or encapsulated stainless steel

Wiring configuration

Type	Description	Precision
2-wires (parasite)	DATA + GND only	✅ Standard
Multi-drop 1-Wire	Several sensors on the same DATA line	🏗️ Low power wide area networks

Self-heating

Very low (< 0.2 °C) due to the low operating voltage.

The DS18B20-PAR can be used for continuous measurement without degradation of accuracy.

Application areas

⚙️ Battery-powered or limited energy systems

💧 Temperature monitoring in humid environments (waterproof versions)

🧠 Long-distance distributed sensors (single cable)

🔋 Minimalist IoT projects (Arduino, ESP, Raspberry Pi)

🧱 Applications without external power (fixed or mobile installations)

Should I choose a KTY84-130 sensor ?

Strengths points

🔋 Ultra simplified diet
→ The DS18B20-PAR operates without a dedicated VDD, using only the DATA line + GND. Ideal for systems where every wire counts: IoT, remote sensors, constrained environments.
🎯 Stable and factory-calibrated precision
→ Same accuracy as the classic version (±0.5 K) despite its parasitic power supply — no loss of performance.
💧 Perfect for waterproof environments
→ Thanks to its 2-wire design, it easily integrates into encapsulated or submerged probes without the need for additional power cables.

Weaknesses points

⚡ Limited current on the bus
→ The 1-Wire bus must provide a stable current during the conversion; otherwise, the measurement may be distorted.
⏱️ Conversion time a bit longer
→ In parasite mode, the full conversion (12 bits) sometimes takes 800–900 ms, slightly slower than the standard version.
📏 Limited cable length
→ The voltage drops increase beyond 15–20 m of cable without external power — to be avoided in extensive installations.

Useful information

Here is some useful information regarding the DS18B20-PAR sensors.

Resolution and precision

The DS18B20-PAR offers the same performance as the classic DS18B20, but draws all its power from the DATA bus.

Its accuracy is guaranteed at ±0.5 K within the useful range, and it maintains a programmable resolution of 9 to 12 bits.

Resolution	No measurement (°C)	Conversion time	Accuracy (−10 → +85 °C)	Extended accuracy (−55 → +125 °C)
9 bits	0,5 °C	93,75 ms	±0,5 K	±1,0 K
10 bits	0,25 °C	187,5 ms	±0,5 K	±1,0 K
11 bits	0,125 °C	375 ms	±0,5 K	±1,0 K
12 bits	0,0625 °C	750–900 ms	±0,5 K	±0,75 K

🔹 Remarks:

Power supply only via the DATA line.
The internal capacitor powers the sensor during conversion.
Low annual drift (±0.2 K/year), identical to the standard DS18B20.
Guaranteed accuracy in the range −10 → +85 °C.

Application example – Reading a DS18B20-PAR

Like all DS18xx sensors, the DS18B20-PAR returns a 16-bit numeric value converted to temperature by the equation:

T(°C) = Raw Value / 16

🔹 Example 1 – Positive Reading

The sensor returns:

LSB = 0xB8
MSB = 0x09

Raw value 0x09B8 = 2488₁₀ T = 2488 / 16 = 155,5 °C

✅ Result: measured temperature ≈ 155.5 °C (simulated value).

🔹 Example 2 – Negative reading

The sensor returns:

LSB = 0xF0
MSB = 0xFF

Raw value (two's complement):

0xFFF0 = -16₁₀ T = -16 / 16 = -1,0 °C

✅ Result: measured temperature = −1.0 °C

🔹 Practical notes:

Reading via the “Read Scratchpad” command (0xBE).
Conversion triggered with “Convert T” (0x44).
Requires a strong pull-up phase (bus held at VDD) during the conversion to recharge the internal capacitor.

Integration into an electronic system

The DS18B20-PAR operates without external VDD, using the data line for its power supply.

This mode significantly simplifies wiring while remaining compatible with the standard 1-Wire bus.

🔹 Typical components

Component	Function
DS18B20-PAR	Parasitically powered 1-Wire digital sensor
Pull resistance (4.7 kΩ)	Maintains the DATA line in a high state
Microcontroller (Arduino, ESP32, Raspberry Pi, STM32)	1-Wire Bus Master
Alimentation	3.3 V or 5 V (via the DATA line only)

🔹 Functional diagram (ASCII)

2-wire connection (parasitic mode)

+3.3V / +5V │ [4.7kΩ] │ DATA ────┼─────────────── DS18B20-PAR │ GND

🔸 The sensor recharges during each "high" period of the DATA signal thanks to an internal capacitor.

🔸 The microcontroller must keep the DATA line = HIGH during the conversion to ensure sufficient power supply.

🔹 Operating principle

1️⃣ The microcontroller initializes the bus with a reset pulse.

2️⃣ The sensor sends back its 64-bit identifier.

3️⃣ The command "Convert T" starts the measurement.

4️⃣ During the conversion, the DS18B20-PAR uses its internal capacitor for power.

5️⃣ After 750–900 ms, the temperature is read via "Read Scratchpad".

Multi-point advantage – Reduced wiring

The parasite mode of the DS18B20-PAR drastically simplifies multipoint installations.

Advantage	Description
Minimal wiring	One single DATA + GND wire for dozens of sensors
Unique ID 64 bits	Each sensor is individually identifiable
Simplified maintenance	No separate power supply or polarity to observe
Full compatibility	Works with all existing DS18B20 libraries