Radical TechMart - Blog #Industrial humidity transmitter

Rotronic HF3 vs HF5 | Humidity Transmitter Comparison

Wed, 21 Oct 2026 06:00:08 +0000

Which Humidity Transmitter Should You Choose: Rotronic HF3 vs HF5?

A maintenance engineer is replacing a humidity transmitter on an air-handling unit. The existing wiring is straightforward, the building management system already accepts a 4–20 mA signal, and the main requirement is stable room or duct monitoring. Should the engineer specify a Rotronic HF3, or move to an HF5?

Now consider a different site: a pharmaceutical facility where the instrumentation team wants more probe flexibility, detailed adjustment options and the possibility of networked monitoring. The answer may be different.

That is the useful way to approach Rotronic HF3 vs HF5. Both families measure relative humidity and temperature and calculate dew point. The decision is less about which model sounds more advanced and more about how the measurement point will be installed, maintained and connected to the rest of the plant.

Rotronic HF3 vs HF5: The Main Difference

The Rotronic HygroFlex HF3 is a practical choice for conventional room, wall and duct measurement points. It uses a fixed-mounted probe and offers analog outputs for monitoring and control. Room-style versions also suit occupied spaces where the instrument should not look out of place.

The Rotronic HygroFlex HF5 is better suited to applications that benefit from a broader choice of compatible HygroClip2 probes, freely scalable analog outputs and optional digital connectivity. It offers additional configuration possibilities for industrial installations.

The important distinction is fixed-probe simplicity versus probe and integration flexibility. Neither should be selected without checking the actual order code.

HF3 vs HF5 Technical Comparison

Selection point	Rotronic HF3	Rotronic HF5
Measured parameters	Relative humidity, temperature and calculated dew point	Relative humidity, temperature and calculated dew point
Probe arrangement	Fixed-mounted probe with polycarbonate housing	Compatible HygroClip2 probes; probe choices vary
RH accuracy at 23°C	±1.5 %RH for wall/duct types; ±1.0 %RH for room Type R	Probe dependent; HC2A-S standard probe listed at ±0.8 %RH
Temperature accuracy at 23°C	±0.2 K	Probe dependent; HC2A-S listed at ±0.1 K
Application temperature	HF3: −40 to 60°C	Probe dependent; transmitter electronics have separate limits
Output options	HF32 4–20 mA; selected three-wire models offer configurable signals	Two freely scalable analog outputs; wiring options vary by model
Digital integration	Analog connections and UART service interface listed	Optional Ethernet, USB, RS485 and wireless-related connectivity
Display	Optional and configurable	Optional graphic display
Mounting	Room, wall, duct and other HF3 forms	Wall and duct versions shown
Enclosure protection	IP rating not stated in supplied HF3 document	IP65 stated in HF5 document

Specifications are based on the supplied Rotronic HF3/HF4 document dated March 2023 and HF5 document dated October 2020. Confirm the selected variant and current manufacturer datasheet before ordering.

Rotronic HF3: When Simple, Direct Monitoring Makes Sense

Imagine a commercial building where a facilities team needs humidity feedback from an AHU duct and a few occupied rooms. If the control panel needs standard analog signals and there is no requirement for interchangeable industrial probes, the HF3 deserves serious consideration.

Best for: Routine HVAC and building climate measurements using a fixed probe and analog signal connection.

Why this model makes sense:

The HF3 gives engineers a straightforward measurement point. The listed humidity accuracy of ±1.5 %RH for wall and duct types, or ±1.0 %RH for the room Type R, helps buyers match the variant to the location.

Its configurable three-wire analog outputs are useful when a BMS or PLC expects a specific voltage or current signal.

Technical points to note:

Measures relative humidity and temperature, with calculated dew point.
HF3 wall and duct accuracy at 23°C: ±1.5 %RH and ±0.2 K.
HF3 room Type R accuracy at 23°C: ±1.0 %RH and ±0.2 K.
HF3 application range: −40 to 60°C and 0 to 100 %RH.
HF32 is a two-wire 4–20 mA variant.
Selected three-wire versions offer configurable voltage or current outputs.
The sensor probe is fixed-mounted, with a polycarbonate probe housing.
Display-equipped versions are available and software adjustment is supported.

Where it is commonly used:

Air-handling unit ducts
Commercial HVAC systems
Office rooms
Museums
Libraries
Warehouse climate monitoring

Selection caution:

Do not assume that every HF3 has the same accuracy, output or physical shape.

A room Type R and a duct version solve different installation problems. Also, the supplied HF3 document does not specify an enclosure IP rating or power supply voltage, so verify both for the exact model.

Rotronic HF5: When Flexibility and Industrial Integration Matter

Consider a production site with several humidity monitoring points, including a ventilation shaft and a technical room.

Some locations may need a different probe body, while others may need readings sent to a plant monitoring system in addition to an analog control loop.

Here the HF5 is often the more appropriate family to evaluate.

Best for: Industrial humidity monitoring where probe choice, output scalability or optional digital connectivity is important.

Why this model makes sense:

With the HF5, the probe is an important part of the selection.

Rotronic lists a standard HC2A-S probe with ±0.8 %RH and ±0.1 K accuracy at 23°C, as well as additional probe types for different environments.

The transmitter offers two scalable analog outputs and, in relevant configurations, optional digital interfaces that can support broader monitoring architectures.

Technical points to note:

Supports a range of compatible HygroClip2 probe types.
HC2A-S standard probe accuracy at 23°C: ±0.8 %RH and ±0.1 K.
Available output families include HF52 two-wire, HF53 three/four-wire and isolated HF54/HF56 variants.
User-scalable analog choices include 0–1 V, 0–5 V, 0–10 V and 0(4)–20 mA.
Optional digital interfaces include Ethernet, USB and RS485.
HF5 electronics are rated −40 to 60°C for HF53/54/56, reduced to −10 to 60°C with an LCD.
The stated enclosure rating is IP65.
The datasheet lists a 2,000-point external memory logging function.

Where it is commonly used:

Pharmaceutical facility monitoring
Food industry utilities
Technical rooms
HVAC ventilation ducts
Printing plants
Paper industry processes

Selection caution:

Do not confuse the temperature capability of a probe with the ambient temperature rating of the transmitter electronics.

Rotronic lists industrial probes with application ranges reaching −100 to 200°C, but that does not mean the transmitter housing can operate at those temperatures.

The datasheet also notes that HF520 transmitters are not compatible with metal industrial probes.

What the Accuracy Figures Really Mean

It is tempting to compare only ±1.5 %RH for an HF3 wall/duct model against ±0.8 %RH for an HF5 with an HC2A-S probe and conclude that HF5 must be the better purchase.

That skips an essential question: What accuracy does the process actually need?

For general building climate control, a properly installed HF3 may meet the project's specified tolerance. For a more demanding humidity measurement point, the HF5 probe options may justify the additional evaluation.

Accuracy figures also depend on the test conditions and selected model.

Installation position, airflow, contamination, condensation and periodic adjustment can influence readings in actual service.

For critical quality systems, define the complete measurement requirement rather than treating one datasheet number as a guarantee of process performance.

PLC, BMS and SCADA Integration: Check the Signal First

Both transmitter families can be considered for analog integration when the selected model and receiving input are compatible.

A 4–20 mA loop can carry an RH measurement to a PLC analog input or a building controller. Voltage outputs are another option in supported configurations.

The difference becomes important when the project requires communication beyond analog signals.

The HF5 datasheet lists optional digital connectivity, including RS485 and Ethernet.

However, RS485 describes a physical interface, not automatically a specific communication protocol.

Confirm the interface option, protocol, wiring and compatibility with your PLC, BMS or SCADA system before purchasing.

One frequent source of confusion is the shared HF3/HF4 datasheet. It lists Ethernet and RS485 models under HF4, not HF3.

Do not assign HF4 networking features to the HF3 by mistake.

Three Practical Selection Scenarios

Office or museum climate monitoring

Consider HF3 room or wall versions if the humidity range, required accuracy, appearance and available analog inputs match the project.

Pharmaceutical or food process monitoring

Consider HF5 where the probe selection, adjustment workflow or integration options fit the site requirement.

Any regulated recordkeeping or compliance claim still needs verification for the full installed system.

High-temperature duct or challenging probe location

Review the HF5 probe range and mechanical installation carefully, then check the separate transmitter electronics limits.

A high-temperature probe does not remove the need to protect the electronics.

Common Mistakes Buyers Should Avoid

Comparing HF3 and HF5 prices without confirming the required output, mounting style and probe.
Applying the HF3 room accuracy specification to every HF3 wall or duct variant.
Assuming all HF5 probes have the same humidity accuracy or temperature range.
Assuming every HF5 includes RS485 or Ethernet as standard.
Confusing the HF3 service UART with an operational plant-network interface.
Ignoring the transmitter ambient limit when choosing a high-temperature probe.
Ordering a replacement without checking wiring, supply, analog scaling and cable entry.
Assuming datasheet accuracy eliminates the need for calibration and maintenance planning.

Do This, Not That

Do this	Not that
Specify room, wall or duct location first	Choose only by HF3 or HF5 model family
Check the exact RH accuracy for the probe and variant	Compare a room HF3 figure with an unrelated HF5 probe
Match the output to the PLC or BMS input	Assume every 4–20 mA device uses identical wiring
Confirm digital option and protocol	Treat RS485 as guaranteed Modbus compatibility
Verify sensor and electronics temperature limits separately	Use probe range as the transmitter ambient rating

Quick Checklist Before Requesting a Quote

Is this a room, wall or duct measurement point?
What are the required RH and temperature accuracy tolerances?
Does the site need a fixed probe or a specific interchangeable probe?
What signal does the BMS, PLC or recorder accept?
Is optional digital communication genuinely necessary?
Which power supply and loop wiring are available?
Will the housing face dust, splashing water or elevated ambient temperature?
Is a local display, adjustment routine or documented calibration required?
What exact model code, probe code and accessories appear on the quotation?

Why Source Rotronic HF3 or HF5 Through Radical TechMart?

The useful starting point is not simply “HF3 price” or “HF5 price.”

A good inquiry states the mounting point, expected humidity conditions, required output and how the reading will be used.

Radical TechMart helps industrial buyers compare instrument options against real application requirements.

For a Rotronic humidity transmitter inquiry, share your existing model if you are replacing a device, together with the output wiring, installation location and any need for network connectivity.

That gives the technical and purchase teams a clearer basis for discussing the right configuration, datasheet, availability and quotation.

Final Thoughts: Rotronic HF3 vs HF5

Choose Rotronic HF3 when a fixed-probe room, wall or duct transmitter meets the measurement and analog integration requirements.

Evaluate Rotronic HF5 when probe flexibility, selectable configurations and optional digital monitoring are part of the project.

The right humidity transmitter is the one that fits the environment, the control system and the maintenance plan.

Paying for functions you do not need rarely improves the installation, while overlooking a critical probe or signal requirement can create trouble during commissioning.

Frequently Asked Questions

1. What is the main difference between Rotronic HF3 and HF5?

HF3 is a fixed-probe transmitter family suited to straightforward climate measurements. HF5 supports a range of compatible probes and offers more configuration and optional digital interface choices.

2. Is Rotronic HF5 more accurate than HF3?

Some HF5 probe combinations list tighter accuracy than the HF3 wall and duct types, but HF5 accuracy is probe dependent. Compare the exact HF3 variant and HF5 probe under the stated test conditions.

3. Can Rotronic HF3 and HF5 connect to a PLC or BMS?

Yes, compatible analog output models can connect to matching PLC or BMS inputs. Confirm loop wiring, supply, output signal and scaling for the selected order code.

4. Does Rotronic HF3 support RS485?

The provided HF3 datasheet lists analog connections and a UART service interface, but not an RS485 network option for HF3. Its companion HF4 family has network-capable variants.

5. Does every Rotronic HF5 include Ethernet or RS485?

No. Digital interfaces are optional and configuration dependent. Verify the exact model and communication option before ordering.

6. Can Rotronic HF5 be used for high-temperature humidity measurement?

Compatible industrial probes have wider stated application ranges, but the probe, extension and transmitter electronics must each be suitable for the installation conditions.

7. Which model should I choose for HVAC duct humidity monitoring?

HF3 may be sufficient for a conventional analog duct point. HF5 is worth evaluating when the installation requires a particular probe, added configurability or optional network connectivity.

8. What should I provide to get a Rotronic HF3 or HF5 quotation?

Share the mounting style, measurement range, accuracy requirement, output signal, power supply, display preference, communication need and any existing part number.

4–20 mA vs 0–10 V Humidity Transmitter

Tue, 20 Oct 2026 19:30:00 +0000

Industrial Selection Guide: 4–20 mA vs 0–10 V Humidity Transmitter

An HVAC contractor installs a humidity transmitter in an air-handling duct. The sensor is reading correctly, but the building management system shows an unexpected value. The problem is not necessarily the humidity sensor. Often, the transmitter's output and the controller's input do not match, or the receiving channel has been scaled incorrectly.

That is why 4–20 mA vs 0–10 V humidity transmitter is a practical selection question, not just a specification to check on a quotation. Both signals can represent the same relative humidity measurement. The better choice depends on cable length, electrical environment, input compatibility and the way maintenance technicians will troubleshoot the installation.

What Does a Humidity Transmitter Actually Send?

A humidity transmitter measures relative humidity using its sensing element, then converts that measurement into an electrical output that a PLC, BMS, indicator or controller can interpret. Some instruments also measure temperature and calculate dew point.

The controller does not receive "55% RH" as words. It receives a signal, such as 12.8 mA or 5.5 V, and converts that signal into a displayed humidity value using the configured measuring range.

For a transmitter scaled from 0 to 100% RH, the two common signal mappings are:

Relative humidity	4–20 mA output	0–10 V output
0% RH	4 mA	0 V
25% RH	8 mA	2.5 V
50% RH	12 mA	5 V
75% RH	16 mA	7.5 V
100% RH	20 mA	10 V

These are example scaling values, not fixed settings for every model. Both the transmitter and controller must use matching ranges.

4–20 mA vs 0–10 V Humidity Transmitter: Key Differences

Selection factor	4–20 mA current output	0–10 V voltage output
Signal principle	Measurement represented by current	Measurement represented by voltage
Typical best fit	Longer cable runs and electrically busy plant areas	Short, controlled runs to compatible HVAC or BMS inputs
Cable resistance	Less sensitive within transmitter compliance limits	Wire resistance and shared return currents can create measurement error
Fault interpretation	A reading below the normal 4 mA range may help indicate faults when supported and configured	0 V can mean minimum measurement or a wiring/power issue
PLC/BMS input	Requires a compatible current input	Requires a compatible voltage input
Wiring	Can be two-wire or separately powered, depending on model	Often separately powered; confirm terminal diagram
Main check	Loop supply, burden resistance and input configuration	Signal common, input impedance, grounding and scaling

Neither output type automatically makes the humidity sensor more accurate. Sensing accuracy comes from the sensor, calibration and installation conditions. Signal choice affects how reliably that measurement reaches the control system.

When a 4–20 mA Humidity Transmitter Makes More Sense

Imagine a pharmaceutical facility where humidity transmitters are installed around production equipment and the control cabinet is some distance away. Cabling may share a route with motor supplies or other electrical services. In that situation, engineers commonly prefer 4–20 mA because a current loop is less sensitive to voltage drops along the cable, provided the transmitter has enough voltage to drive the total loop resistance.

The 4 mA live zero also helps with troubleshooting. For a correctly scaled 0–100% RH transmitter, zero humidity is represented by 4 mA, not 0 mA. A near-zero current can therefore point to an open circuit, power loss or other fault. The controller must be configured to recognize the abnormal signal, and the instrument's fault behavior must be confirmed.

Best for: Plant monitoring points, longer wiring runs and PLC installations that already use analog current input modules.

Selection caution: A current-output transmitter is not automatically a two-wire loop-powered transmitter. Confirm its supply and terminal arrangement before planning the panel wiring.

When a 0–10 V Humidity Transmitter Is a Practical Choice

A duct-mounted humidity transmitter may sit only a few metres from an HVAC controller equipped with 0–10 V analog inputs. If the cable path is short, the signal reference is properly managed and the controller expects voltage, a 0–10 V humidity transmitter can be a sensible solution.

Voltage outputs are commonly encountered in HVAC and building-control systems. They are easy to interpret during commissioning: a correctly scaled 5 V signal corresponds to 50% RH when the configured span is 0 to 100% RH.

However, the receiving input must have suitable impedance, and the signal common needs proper wiring. On longer runs, voltage drop, induced interference or differences in ground potential can affect the reading.

Best for: Nearby HVAC controllers and BMS devices with native 0–10 V inputs.

Selection caution: Do not assume an unused analog input accepts both voltage and current. Check the BMS controller's input specification and configuration.

A Real Product Example: Rotronic XB32A OEM Humidity Transmitter

For OEM machine builders, the Rotronic XB32A is a useful example because it illustrates how output choice can be built into the transmitter configuration rather than treated as a completely different sensor family.

The XB32A is supplied as an OEM PCB with a fixed cable probe and no external electronics housing. Rotronic specifies two freely selectable, scalable analog outputs. Its listed choices include 0–1 V, 0–5 V, 0–10 V and 0(4)–20 mA. It also measures temperature and calculates dew or frost point, depending on configuration.

Best for: OEM humidity monitoring inside appropriately protected machinery, environmental chambers, drying equipment and pharmaceutical equipment assemblies.

Why this model makes sense: An equipment manufacturer can select a signal that matches the receiving controller rather than changing the entire measurement design. The XB32A is explicitly a three-wire instrument, including when configured for 4–20 mA output.

Technical points to note:

Power supply: 15–40 VDC or 12–28 VAC.
Signal outputs: Two user-scalable analog outputs.
Listed output options: 0–1 V, 0–5 V, 0–10 V and 0(4)–20 mA.
Humidity accuracy at 23°C: ±1.0% RH.
Temperature accuracy at 23°C: ±0.2 K.
Humidity measuring range: 0–100% RH, non-condensing.
Maximum listed current-output load: 500 Ω.
Listed voltage-output load requirement: ≥1 kΩ per volt, so a 0–10 V configuration calls for a load of at least 10 kΩ.

Where it is used: Environmental chambers, incubators, drying systems, pasteurization equipment and OEM pharmaceutical equipment.

Selection caution: Because the XB32A is a bare-board OEM transmitter, the equipment designer must confirm enclosure protection, wiring, probe placement and supply arrangements. Its probe and electronics have separate temperature limits. Check the specific datasheet and ordering code before purchase.

PLC and BMS Scaling: A Small Error That Creates Big Confusion

Suppose the transmitter is scaled for 0–100% RH but the PLC channel expects 0–20 mA rather than 4–20 mA. At 12 mA, the transmitter intends to communicate 50% RH, but a controller scaled as 0–20 mA could display 60% RH instead.

The transmitter may be functioning perfectly. The configuration is wrong.

During commissioning, verify the sensor's measured range, transmitter output range, receiving input type and software scaling. For a 0–10 V installation, also check the signal common. For 4–20 mA, confirm the loop wiring and available compliance voltage.

Does a Humidity Data Logger Replace a Transmitter?

Not necessarily. The supplied Rotronic HL-1D manual describes a humidity and temperature data logger, not a 4–20 mA or 0–10 V process transmitter. It records readings internally, uses a CR2 battery and connects to a PC through mini-USB for configuration and data download with Rotronic HW4 software.

That makes it relevant when the real requirement is independent monitoring, a recorded humidity history or spot-checking environmental conditions. It should not be specified as a direct analog replacement for a transmitter feeding a PLC or BMS.

In a pharmaceutical monitoring project, the team may need both continuous transmitter signals for control and separate logging for records. Decide which job each device must perform.

Common Mistakes to Avoid

Buying a 4–20 mA transmitter for a voltage-only PLC input.
Assuming every 4–20 mA device is loop-powered and uses only two wires.
Ignoring voltage-input grounding and common-reference wiring.
Configuring a PLC channel for 0–20 mA when the transmitter sends 4–20 mA.
Forgetting the loop burden or the minimum voltage-input impedance.
Selecting output type before considering cable routing and electrical noise.
Assuming output signal type determines humidity accuracy.
Specifying a data logger when the controller needs a continuous analog signal.

Do This, Not That

Do this	Not that
Match the transmitter signal to the receiving analog input	Assume every PLC accepts every signal
Consider cable distance and electrical environment	Select only by the lowest product price
Verify supply, terminal wiring and load	Assume all current outputs are two-wire
Configure matching transmitter and PLC ranges	Leave scaling at an unsuitable default
Use a logger when historic records are required	Expect a logging device to provide an unspecified analog output

Quick Selection Checklist

Is humidity being used for control, indication, recording or a combination?
Does the PLC or BMS accept 4–20 mA, 0–10 V or both?
How far is the transmitter from the receiving controller?
Will the cable pass near drives, motors or other interference sources?
Is the transmitter two-wire or separately powered?
Are loop resistance and voltage-input impedance within limits?
Are the transmitter and controller scaled to the same RH range?
What sensor accuracy, calibration and enclosure requirements apply?
Does the project also need a separate humidity data logger?
Has the exact manufacturer datasheet been checked?

Why Source Humidity Instruments Through Radical TechMart?

A quotation request that simply says "humidity sensor required" leaves too many engineering questions unanswered. The maintenance team needs a reliable reading, the automation engineer needs the correct signal, and procurement needs the right model and configuration.

At Radical TechMart, the objective is to help customers compare humidity instruments for their actual applications, including HVAC, industrial monitoring and OEM equipment. Share the mounting location, output type, supply voltage, measuring range and receiving controller details so the right configuration can be evaluated before ordering.

Final Thoughts

For 4–20 mA vs 0–10 V humidity transmitter selection, start with the receiving system and installation conditions. Choose 4–20 mA when current inputs, longer cable runs or industrial electrical conditions make it the stronger fit. Choose 0–10 V when the controller is designed for voltage signals and the installation is short and properly wired.

A correct humidity measurement is useful only if the receiving system interprets it correctly. The signal, wiring and scaling deserve as much attention as the sensor itself.

Frequently Asked Questions

1. Which is better for industrial humidity monitoring, 4–20 mA or 0–10 V?

For longer cable runs or electrically noisy plant areas, 4–20 mA is often preferred. For short connections to compatible HVAC or BMS inputs, 0–10 V can work well.

2. Is a 4–20 mA humidity transmitter more accurate than a 0–10 V transmitter?

Not inherently. Sensor accuracy depends on the sensing element, calibration and installation. Output selection mainly affects transmission and interface compatibility.

3. Can a 0–10 V humidity transmitter connect to a PLC?

Yes, if the PLC has a compatible voltage analog input and the wiring, common reference and engineering scaling are correct.

4. Why does 4–20 mA start at 4 mA rather than 0 mA?

The 4 mA live zero represents the lower measurement limit while helping compatible control systems distinguish normal minimum readings from some wiring or power faults.

5. Can Rotronic XB32A be configured for both 4–20 mA and 0–10 V?

The XB32A supports freely selectable and scalable analog output types, including both of these ranges. Confirm the exact output assignment and configuration for the selected unit.

6. Is the Rotronic XB32A a two-wire loop-powered transmitter?

No. The supplied manufacturer's datasheet identifies it as a three-wire OEM transmitter, even though it supports current outputs.

7. Is the Rotronic HL-1D a substitute for a 4–20 mA humidity transmitter?

No. The HL-1D is a battery-powered logger that stores humidity and temperature data for later download. Its supplied manual does not specify a continuous 4–20 mA or 0–10 V output.

8. What details should I send when requesting a humidity transmitter quotation?

Provide the humidity range, required accuracy, mounting and environment, output type, supply voltage, distance to the controller, input specifications, display needs and calibration requirements.