Digital Overhead Stirrer with Torque Display

What is the Digital Overhead Stirrer with Torque Display?

This overhead stirrer measures motor torque, shows it with speed and time on a digital display, and offers a PC interface for logging. It is chosen for process development, scale-up and any work where viscosity change during mixing must be tracked and documented.

Overview

A digital overhead stirrer with torque display combines closed-loop speed regulation with direct or calculated torque measurement. Torque in N·cm, speed in rpm and elapsed time appear on a large display, and the controller can store set programs with speed ramps. An RS-232, USB or analog output streams data to laboratory software or a recorder, which lets the user plot torque against time as a viscosity proxy. Torque range is typically 5 to 200 N·cm with resolution of 0.1 to 1 N·cm and accuracy of about ±1 to 3 percent of full scale. Additional functions include minimum and maximum torque limits that stop the stirrer, speed ramps and timers. Compared with basic units, it adds data capability rather than torque alone, which is valuable in regulated development work.

How does it work?

An overhead stirrer mounts on a laboratory stand or clamp above the vessel and transmits rotation through a chuck to a shaft with an impeller. The motor is usually brushless DC or brushed DC, sometimes with a planetary gearbox, and the controller regulates speed using a tachometer or Hall sensor. Because torque equals force times radius and power demand rises with viscosity, stirrer selection is based on torque (N·cm) and viscosity capacity rather than wattage. Many models measure motor current or use a torque sensor to show torque on the display, which helps monitor viscosity changes during reactions such as polymerization. Impeller geometry determines the flow pattern: propeller and pitched-blade impellers give axial flow, anchors and helical ribbons suit viscous media near the wall, and turbines or dissolver discs generate radial shear.

What are the key features?

• Direct torque measurement with display in N·cm
• Programmable speed ramps and timer for reproducible methods
• RS-232 or USB output for torque and speed logging
• Adjustable upper and lower torque limits stop the drive automatically
• Closed-loop speed regulation with low-speed accuracy
• Large display showing speed, torque and time simultaneously

What are the technical specifications?

A typical digital overhead stirrer with torque display configuration offers speed range of 10–2,000 rpm, torque range of 5–200 N·cm, torque accuracy of ±3 % of full scale, torque resolution of 1 N·cm, speed accuracy of ±1 rpm and max viscosity of 50,000 mPa·s. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Digital Overhead Stirrer with Torque Display is used in process development and scale-up, viscosity-change monitoring during polymerization, gelation and curing studies, documented formulation work and rheology screening of suspensions. Across the wider Overhead Stirrers class, laboratories also deploy it for polymer synthesis and resin mixing, coatings and adhesive formulation and pharmaceutical suspension and ointment preparation.

Which standards and certifications apply?

Relevant standards and methods include IEC 61010-1, IEC 61326-1, GB 4793.1, ASTM D2196, ISO 2555 and ISO 9001. Certification candidates for this model are CE, RoHS and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Mount the stirrer on a rigid stand so the shaft runs concentric with the vessel, and clamp the vessel independently. Always increase speed gradually and use a stirring guard or splash shield. Inspect shafts for bending and wear of the chuck, since imbalance causes vibration and shaft whip. Keep the motor housing away from solvent vapors unless it is approved for the environment. Clean impellers promptly so dried residue does not cross-contaminate. Verify speed and, if fitted, the torque display at intervals using a reference tachometer or torque gauge. Confirm electrical safety to IEC 61010-1 and ensure that the emergency stop or overload cutoff operates correctly.

How do I select the right Digital Overhead Stirrer with Torque Display?

Select this variant when torque data must be displayed, limited or recorded, for example in scale-up, polymerization end-point detection or documented formulation work. For simple mixing a basic model is more economical. Specify torque range and resolution, interface type, logging software needs and calibration documentation.

How does it compare with other Overhead Stirrers variants?

The decisive parameter is maximum torque at the working speed, together with the viscosity and volume of the fluid. As a rule of thumb, small units of 20 to 60 N·cm cover up to a few liters of medium viscosity, while 100 to 400 N·cm models handle tens of liters or pastes above 50,000 mPa·s. Choose the speed range to suit the impeller: low-speed high-torque for anchor and ribbon, high-speed for dispersion. Check whether the unit measures torque and offers a data interface if process monitoring is needed. For flammable atmospheres or reactor jackets, consider air motors or explosion-protected drives. Also verify chuck capacity, compatibility with stand and clamp, shaft sealing options for reactors, and that the controller protects against overload. Include viscosity range, vessel diameter and target rpm in the inquiry.