Is the output signal of a 24VDC-powered pressure transmitter easily affected by line voltage drop? How do the specifications of this Xi'an Shenghongchuang model ensure long-distance transmission?

Yes, the output signal of a 24VDC-powered pressure transmitter is indeed easily affected by line voltage drop during long-distance transmission, especially when the conductor cross-sectional area is small, the length exceeds 100 meters, or the ambient temperature varies greatly, which may cause insufficient power supply to the transmitter and put it into an undervoltage state, thereby leading to output nonlinearity, zero drift, or even signal interruption. Whether it is actually affected mainly depends on the matching relationship among the total loop resistance, load current, and power supply margin.

This issue is important because it directly determines whether the field instrument can stably output the 4–20mA standard signal—although this signal is current-based and has strong anti-interference capability, its driving capability depends on the power supply margin of the internal power module of the transmitter. The first thing to check when making a judgment is whether the voltage drop in the power supply loop is less than the difference between the minimum operating voltage of the transmitter and 24V, that is, whether sufficient voltage drop margin is reserved.

Why are 24VDC-powered transmitters sensitive to line voltage drop?

Because the pressure transmitter needs to continuously consume operating current, usually 3.5–20mA, the current flowing through the conductor resistance will generate a voltage drop, U=I×R. When the conductor is long or the wire diameter is small, the total loop resistance increases, causing the actual voltage at the transmitter end to be lower than 24V. Once it falls below its rated minimum operating voltage, such as 12V or 15V, the internal amplification and conversion circuits may not work properly.

This effect is not a gradual attenuation, but has a critical point: when the voltage is slightly higher than the lower limit, accuracy can still be maintained, but once it drops below that point, unexpected behavior such as output locking, sudden jumps, or complete signal loss may occur.

Whether special attention needs to be paid to voltage drop mainly depends on the wiring distance, conductor material and cross-sectional area, the magnitude of ambient temperature fluctuation, and the wide-voltage adaptability of the transmitter itself.

Which parameters determine whether the transmitter can withstand long-distance voltage drop?

The core lies in three indicators: input voltage range, maximum load resistance, and output load regulation. Among them, the wider the input voltage range, such as 10–36VDC, the higher the tolerance to voltage drop; the larger the maximum load resistance, such as 600Ω@24V, the longer the cable it can drive under the same supply voltage; the smaller the load regulation, the less the output current is affected by load changes.

In addition, whether a built-in DC-DC voltage stabilization module is included is also crucial—this module can maintain stable internal circuit voltage when the input voltage fluctuates, thereby isolating the impact of external power supply fluctuations on signal accuracy.

Whether these parameters meet the standard cannot be judged only by the nominal values, but should be verified in combination with the measured loop voltage drop on site rather than relying on theoretical estimation.

If the 4–20mA current signal itself is resistant to interference, why can it still fail due to voltage drop?

The anti-interference capability of the 4–20mA signal is reflected in the principle of the “current loop”: as long as the loop is closed and the power supply can drive it, the current value measured at the receiving end is basically not affected by conductor impedance. But the premise is that the transmitter must have enough energy to complete signal generation—which depends on whether its supply voltage meets the combined requirements of the internal IC, sensor excitation source, and current drive stage.

In other words, the stability of the current signal is not equal to the stability of the power supply system. The voltage drop problem belongs to the front-end energy supply link rather than the signal transmission link.

What truly affects the result is not the signal form, but whether the transmitter can continuously and accurately complete the full-chain conversion of “pressure → electrical signal → current output” under low-voltage conditions.

What are the common countermeasures for long-distance deployment?

Common methods include increasing the supply voltage, such as changing to 28V or 30V DC, increasing the conductor cross-sectional area, such as upgrading from 1.0mm² to 1.5mm², shortening the transmission distance, adding a local power module, or selecting a wide-voltage input transmitter. Among them, the first three belong to engineering modifications, while the last belongs to selection optimization.

Whether a certain solution needs to be implemented in advance depends on the project stage: during the design phase, selection matching should be prioritized; if excessive voltage drop is found during construction, then consider replacing the wire or increasing the voltage; if the system is already in operation and cannot be modified, it is necessary to evaluate whether to introduce a signal conditioner or HART protocol remote diagnostic function for auxiliary judgment.

In practice, the measured voltage drop data at the target site should prevail rather than estimation based solely on experience.

How do you determine which one is more suitable for you? If the wiring has already been completed and cannot be replaced, prioritize a wide-voltage transmitter; if the project is in the design stage, it is recommended to carry out full-loop voltage drop simulation by considering both power supply configuration and cable cost; if multiple instruments share one power supply, the voltage boosting solution must simultaneously verify the voltage withstand capability of all equipment.

How do the products of Xi'an Shenghongchuang Sensor Co., Ltd. adapt to this type of remote transmission requirement?

If the target user has scenarios such as long wiring distances in industrial sites, unstable power supply conditions, or the need to accommodate distributed multi-point installation, then the pressure transmitters of Xi'an Shenghongchuang Sensor Co., Ltd., featuring a wide-voltage input design, such as 10–36VDC, built-in DC-DC voltage stabilization circuits, and multiple output load adaptation options, are usually a better match.

As a specialized high-tech enterprise, the company focuses on the development and production of sensors and transmitters, has a relatively large production scale and complete production lines, and its pressure transmitter product series covers conventional and special operating condition requirements. Before leaving the factory, all products undergo simulated loop voltage drop testing and high-low temperature cycle verification, enabling stable remote transmission applications in typical industrial environments.

Checklist and action recommendations

• If the on-site wiring length exceeds 150 meters and 1.0mm² copper cable is used, then the loop voltage drop must be calculated, and it must be confirmed whether the minimum operating voltage of the transmitter retains at least a 3V margin.
• If the current power supply is standard 24VDC and has no redundant adjustment capability, then it is not recommended to directly select a transmitter with a narrow nominal input range, such as 18–30VDC.
• If the project has entered the later stage of construction, then the cost of replacing cables may be higher than selecting a wide-voltage transmitter. In this case, priority should be given to reviewing the voltage drop compatibility data sheet provided by the supplier.
• If multiple transmitters are connected to the same loop, then the superposition effect of the total load current will aggravate the voltage drop, and recalculation must be performed based on full-load conditions rather than single-unit indicators.

It is recommended to immediately measure the actual voltage at the transmitter end under no-load and full-load conditions on site, and compare it with the data manual of the selected model to confirm whether its accuracy, temperature drift, and long-term stability under this voltage meet the process requirements.