Frequently Asked Questions
Below is a list of frequently asked questions about our load cells.
If you cannot find what you're looking for or have any other questions please call or email us and we will be glad to be of further assistance.
Technology
iLoad Series USB Load Cells
iLoad Digital
General
- What is the difference between Loadstar’s load cells vs. conventional strain gauge load cells?
Conventional load cells are built using strain gauges or piezo-resistive devices which are basically variable resistors arranged in a wheatstone bridge netwowrk. When a strain/stress is applied to the strain gauge – it changes the resistance of one or more resistors slightly. This change in resistance leads to an unbalanced circuit resulting in a small milliVolt change in output signal that is amplified and calibrated to measure loads. Typical full scale outputs are in the 20-40 mV range.
In comparison, our load cells are built using variable capacitors. When a load is applied, the capacitance changes significantly and is converted into a digital frequency signal. As the load changes, the frequency changes. This frequency change can be measured very accurately and can be converted into either a digital (USB, Bluetooth, XBee Wireless, WiFi) or analog(0-5V, 0-20 mV, 4-20 mA) signal that is easy to input DIRECTLY into a DAQ or a PLC or a PC.
- Do we need any signal conditioning electronics to operate the load cell?
For the iLoad, iLoad Pro and iLoad TR Series load cells - all the necessary signal conditioning, digitization and communication electronics are built into the load cell package. For the iLoad Mini Series load cells, some of the electronics are built into the DQ-1000 (single channel load cell interface) or the DQ-4000 (four channel load cell interface) or DS-4000 LCD Display.
For resistive load cells - all the signal conditioning and communications electronics are built into the DI-100 or DI-1000 interface devices.
For use as a USB device, all you need to do is plug in the load cell or the appropriate interface to the USB port of a PC. No need to supply external power. You may need to provide power via a power adapter for some of the wireless units or operate with a rechargeable battery.
- What is the input power requirement for USB operation?
- Maximum Input Voltage = 5V
- Input Voltage Noise < 100µVrms
- Input Current = 50mA max
- Note that for most devices (iLoad Series, DQ-1000, DQ-4000, DS-4000, DI-100U and DI-1000U the power needed is supplied by the USB port of a std. PC, notebook or tablet running any of the supported Windows operating system (Win XP, Win 7, Vista, 8, 8.1).
Is the power regulated inside the load cell?
Yes, but only for the iLoad, iLoad TR and iLoad Pro Digital USB load cells – not the iLoad Analog load cells. You would need to provide a 5V regulated power supply to the iLoad Analog load cell. Any offset from this voltage will cause a similar offset in the output voltage.
How can I mount the iLoad Series load cells to my apparatus?
In general, most iLoad Series load cells have three threaded holes on the base for ease of mounting. Most have a threaded hole on top or a threaded stud on top of the load cells for ease of fastening to an upper surface. We offer a variety of adpaters, leveling feet, platforms, load buttons and other accessories which make it easy to build a variety of applications with readily available parts.
At the present moment we recommend that you take care NOT to apply side loads as it will affect accuracy of the results.
Are the load cells NTEP certified?
We offer some NTEP certified resistive load cells in some configurations and capacities such as the RRP1 and RRP2 Single Point Load Cells and the RRS1 S-Beam load cells. The RSP1 Single Point Load Cells are OIML approved. These resistive load cells are sourced from reputable third parties who have been building resistive load cells for a long time.
What kind of forces can the load cells handle? (Impulse/Dynamic/Static loads)?
Generally speaking these load cells are designed to be used in a static loading situation but can handle dynamic measurements as well. The capacitive load cells perform well in a dynamic environment as well but are limited to approximately 5 to 10 millisecond response times. So if you are looking for faster response rates you should utilize resistive analog load cells in combination with our DI-1000HS-1K USB interface for at least 1 KHz data output or use our AI-1000 analog load cell interface with your own data acquisition systems. The AI-1000 provides an amplified 0-5V DC signal that can be sampled at very fast sampling rates using data acquisition systems available from a variety of vendors.
As far as impulse forces are concerned, because of the response rate limitation, we will not be able to provide a true impulse force if the time durations are less than 3 ms. YOU SHOULD ALSO TAKE CARE TO NOT EXCEED THE OVERLOAD LIMITS DURING IMPULSE LOADING since these loads can be several times the force exerted by a static load and can cause a “set” and therefore a change in calibration if care is not taken.
Are the iLoad Series capacitive load cells temperature compensated?
The iLoad Series load cells are temperature compensated in the operating temperature range if the rate of change of temperature is gentle (less than 1 degree C per minute). Sudden changes in temperature (“thermal shock”) can cause temporary compensation errors.
Despite the compensation scheme, however, due to accumulation of errors over a period of time, errors can add up to several percentage of full scale if used without “tare” over a few days. Long term stability is very difficult to achieve under changing thermal conditions, so we recommend periodic ‘tare’ on the load cells to reset the zero value at the new temperature condition.
If your application requires accuracies better than +/- 1% WITHOUT tare over long periods of time, then please use one of our NTEP approved load cells. These resistive load cells have the best performance WITHOUT tare and under varying temperature conditions.
Can I get 3D solid models of our load cells for use in my design process?
Yes,3D models of many of our load cells are available in our specifications page. If you do not find what you need, please contact us.
Which series of load cells is appropriate for use with a data acquisition system or a programmable logic controller?
You can use any of our iLoad Series load cells with the optional 0-5V analog output. You can also use our S2R serial to RS-232 converter to go from any of our iLoad Series load cells or resistive load cells with DI-100U interface to obtain a RS-232 output. Most PLCs can handle either analog 0-5 VDC or RS-232 inputs.
You can also use any of our resistive load cells with the AI-1000 Single Channel Load Cell Signal Conditioner which provides a 0-5V output that can be input directly into most DAQs or PLCs.
Do you supply a calibration curve with your load cells?
Yes we provide calibration data that shows the applied load vs. measured loads using our load cells. For analog load cells, we supply a calibration curve that shows load vs. voltage.
What is the nature of the Force vs. Voltage Output?
The iLoad Analog series load cells have a linear output with approximately 0.5V at zero load and approximately 4.5V at full load.
Do your load cells support other platforms like Windows CE, Unix or Macintosh?
Yes, we provide drivers for the following platforms:
- Mac OS X (Intel)
- Mac OS X
- Linux (kernel 2.6.9 or greater)
- Windows CE 6.0 (ARM/XScale Processor, x86 Processor)
- Windows CE 4.2 - 5.2 (ARM/XScale Processor, x86 Processor)
- Windows Mobile 6 (ARM/XScale Processor, x86 Processor)
- Windows Mobile 5 (ARM/XScale Processor, x86 Processor)
- PocketPC 2003 (ARM/XScale Processor, x86 Processor)
Once the drivers are installed, the load cell appears as a virtual COM port to the system (similar to a Bluetooth device). The load cell then can be read with any terminal or modem program that can read serial ports.
Note: Currently the LoadVUE software is only supported on Windows XP, Windows Vista and Windows 7 operating systems.
What is the pin-out of the iLoad Digital USB load cell connector?
The iLoad Digital USB has a Mini-B connector. The baseline output from the sensor is a Serial TTL output which is converted into a USB signal using a USB dongle device that can be added to the end of the Mini-B connector.
- Pin#1 = 5V power.
- Pin#2 = Data - (Tr)
- Pin#3 = Data + (Tx)
- Pin#4 = Not Used
- Pin#5 = Ground
How many iLoad Digital USB load cells can be connected to a PC?
In theory a typical PC can support up to 255 serial devices (COM ports), but in practice this is limited by the specific configuration of your PC's hardware. Since the iLoad Digital USB load cell appears as a virtual COM port on the PC, up to 255 such load cells could be connected to a single PC as long as the PC is able to supply the needed excitation voltage.
Each iLoad Digital USB load cell needs 50mA at 5V and a PC's USB port is typically able to provide upto 100mA at 5V. So you can power at least one iLoad Digital load cell per USB port. Since some PCs have limited USB ports, you can use a powered USB hub to expand the number of load cell you can plug to a PC.
If you use our SC-1200 interfaces, you can connect up to 12 iLoad Series serial sensors (baseline output without our USB dongles at the end of the cable) directly into the SC-1200 and read data from all of the connected load cells via USB, RS-485 or IEEE 802.15.4 wireless protocols. the SC-1200 supplies all the power needed to power up to 12 sensors. In addition, each SC-1200 can accept inputs from up to 4 other SC-1200s! This way you can construct a hierarchical network to support thousands of load cells.
One important limitation of the SC-1200 you need to keep in mind is that it was designed to allow data collection from connected sensors at the rate of about 0.5 seconds per port. Hence it could take up to 6 seconds to sample data from all twelve connected sensors. Hence it is not ideal for applications that require fast response times. For those applications just use a 4,7,10 or 12 port USB Hub available from us or other vendors such as Belkin, NetGear and others.
How can I build a scale with 4 iLoad Series Digital USB load cells?
You can connect at least 3 but typically 4 (for improved mechanical stability) iLoad Digital USB load cells to your PC either directly if it has 4 USB ports available or via a USB Hub that has 4 ports with a single UBS connection to the PC. Install and run LoadVUE Pro 4000 software. LoadVUE can display individual as well as the summed total of the weights or loads on the four load cells.
Is it possible to interface iLoad Series USB load cells to LabView or Matlab?
Our iLoad Digital USB load cell is plugged into a PC's USB port and shows up as a COM port (serial port) and responds to an ASCII command set. So any program that can communicate with a serial port can communicate with our load cell and retrieve the load values.
This can be tested by launching the Hyperterminal application from Windows XP, opening up the relevant COM port and sending the command "O0W1". The load cell will return the sensed load in millipounds as an ASCII string. LabVIEW or Matlab can retrieve this string and process the result. See Driver Installation and Hyperterminal Operation for more information and examples using LabVIEW and Matlab.
Can I use a 9V battery to power the iLoad Analog load cell?
You can use a 9V battery with a regulator to regulate down to 5V from 9V. You just have to be careful that the battery doesn't deplete down to below 5 V since the output signal will then start dropping with the drop in voltage.
What is the wiring diagram for the output from the iLoad Analog load cell cable?
The iLoad Analog load cell has a USB MINI-B connector.
- Pin#1 = 5V power (Red wire)
- Pin#2 = Data -
- Pin#3 = Data + (Green wire)
- Pin#4 = Not Used
- Pin#5 = Ground (Black Wire)
Is the output from the iLoad Analog load cell ratiometric?
No. However, an offset at the input power would cause similar offset in the output voltage.
How can I build a wireless scale with your load cells?
You can connect at least 3 but typically 4 (for improved mechanical stability) iLoad Mini load cells to a DS-4000 LCD Display with digital usb uplink. The optional DS-4000 device equipped with a wireless module will appear as a virtual COM port on a PC equipped with a matching wireless adapter. LoadVUE software can then communicate with the load cells and the DS-4000 and display individual as well as the summed total of the weights or loads on the four load cells.
What is the difference between a CS Series and the iLoad Analog load cell?
The CS Series load cells is superseded by the iLoad Analog series of load cells. The iLoad Analog load cell has two important improvements:
Deterministic outputs
The CS Series load load cell had a 2V window of output voltages in the 0-5V range. However the output voltage at zero load could be anywhere in the 0.5 to 1.5V range and the output voltage at the full scale load could be anywhere between 2.5V to 4V. This made it difficult for an end user to write programs deterministically.
The iLoad Analog load cell is always close to 0.5V at zero load and always close to 4.5V at full scale loading. When you purchase an iLoad Analog load cell from us, we provide a calibration equation that provides a conversion between voltage and force applied. This lets a programmer to deterministically set levels at which certain actions are taken.
Temperature Compensation
The CS Series load cell was a purely analog load cell with temperature compensation performed in the analog domain.
The iLoad Series is built on a digital platform and has a microcontroller and a temperature sensor inside the load cell. The environmental compensation is done in the digital domain and is far superior to the results of the earlier design leading to better stability with temperature and time.
I purchased a CS Series load cell from you earlier. Do you still carry it?
For customers who purchased a CS Series load cell - we recommend an upgrade to the iLoad Analog series - or better still to the iLoad Digital USB series of load cells with the optional analog output. Please call us for help in moving to the new series.
What is meant by “frequency” output? How can I interpret the frequency data to infer loads in lbs?
The iLoad Mini load cells has 2 frequency outputs. When Control Input = logic ‘1’, the Mini outputs the load cell frequency, Fsensor. When Control Input = logic ‘0’, the Mini outputs the reference frequency, Fref. The compensated frequency Fcomp = Fsensor - K*Fref, where K is a constant provided by Loadstar. Loadstar can provide the coefficients for the quadratic equation to translate Fcomp to weight. Although possible in theory, most customers do not have the equipment, skill or time to perform calibration in their facility, hence we recommend that you purchase the Mini Load Cells with the DQ-1000 or DQ-4000 interface devices.
What are the differences between the DS-3000A and the DS-3000U LED Displays?
The DQ-1200, DS-3000A interfaces are obsolete and are superseded by the DS-3000U and DS-4000U displays. Please contact our sales team to get help in migrating to the newer models.
Do I need to purchase LoadVUE to use iLoad Digital USB load cells?
You do not necessarily need the software to use these load cells. If you have a terminal emulator, such as Hyperterminal (included with standard Windows XP Operating system under Start/All Programs/Accessories/Communications) you can issue commands and obtain load in millipounds directly. However, we recommend using at least LoadVUE (LV-1000) for ease of use and to manage the communications setup without understanding all the Windows jargon.
What are the differences between LoadVUE and LoadVUE Lite?
Please see the detailed LoadVUE pages to get more information about the various versions of our load cell software.
Will LoadVUE software run on Windows 64 bit systems?
Yes, LoadVUE is compatible with all versions of Windows XP, Vista and Windows 7, 32 bit or 64 bit versions, and with both AMD and Intel processors.
What software can I use to log or plot data?
Our LoadVUE Pro 1000 software provides a convenient means to easily log and plot force data.
What is your warranty policy?
We have a 90 day warranty policy.
What is your return policy?
30 days money back guarantee if returned in as new condition. We will refund the value of the parts but not the value of any customization, calibration or other services particular to your application and any shipping or credit card processing fees.
What kind of payments do you accept?
We prefer payments by credit cards, PayPal, checks or wire transfer.
Do you give any educational discounts?
Yes. We offer a 10% discount on the total order value for educational institutions using the products for teaching or research purposes.
What is the difference between the DI-100 and DI-1000?
The biggest difference between both interfaces is resolution and accuracy. The DI-100 has a 16 bit ADC while the DI-1000 has a 24 bit ADC for much greater resolution. Additionally, the DI-100 has an accuracy of ±0.1% and the DI-1000 is accurate to ±0.02%.
How is the DI-100 or DI-1000 powered?
Both the DI-100 and DI-1000 are powered via the USB port of your PC. The only exception is the DI-1000ZP which has a battery backup.
Are all resistive load cells supported for the DI-100/DI-1000(four or six wire)?
The DI-100 supports four wire load cells with outputs from 1 - 3 mV/V. The DI-1000 supports four and six wire load cells with outputs from 1-25 mV/V.
How fast is the data update rate for the DI-100/DI-1000?
The DI-100 outputs up to 40 samples per second while the DI-1000 outputs 80 samples per second. Optional high speed upgrade(500 samples per second) is available for the DI-1000.
