Weighbridge Training Course Beijing - September 2017 Zero Setting Devices

Zero setting devices A zero setting device is a device for setting the indication to zero when there is no load on the load receptor The following are zero setting devices found on NAWI: Semi automatic zero-setting device Non-automatic zero setting device Zero tracking Automatic Zero setting device

Zero setting devices Semi automatic zero setting device Device for setting the indication to zero automatically following a manual command ( zero button) Non automatic zero setting device Device for setting the indication to zero by the operator Zero tracking device Device for maintaining the Zero indication within certain limits automatically Automatic zero setting device Device for setting the indication to zero automatically without the intervention of the operator Equilibrium is stable means = it can maintain the reading / maintain the accuracy requirement

Zero setting devices Zero setting requirements The effect does not alter maximum capacity The accuracy is ± 0.25e The range is 4% of max for zero setting and zero tracking Equilibrium is stable means = it can maintain the reading / maintain the accuracy requirement

Zero setting devices Zero tracking device To test zero tracking: Reset the instrument to zero using the zero setting device Apply a load of 1e to the load receptor If after 5 seconds the indicator changes and stabilises at 1e :Pass remains on zero : Fail

Zero setting device accuracy Non-Automatic and Semi-automatic zero -setting device To test non-automatic and Semi-automatic zero setting: Apply a load that is within the range of the instrument. This range varies between 0 to 4% of maximum capacity , in most cases it will be ± 2% around zero Add small additional loads of 0.1e to take the load just below the next change over point Zero the instrument using the zero setting device ( zero button) Ensure that: The numerical indicator displays zero

Zero setting device accuracy The zero indication lamp or enunciator is illuminated Apply a load of 10e Lightly apply an additional 0.25e If the instrument changes and stabilises at +1e from the original indication the instrument fails If the indication remains unchanged firmly apply an additional 0.5e If the indication changes and stabilises at +1e from the original indication the instrument passes If the indication remains unchanged the instrument fails

Zero setting device accuracy (cont’d)

Zero setting device accuracy Automatic Zero setting To test automatic zero setting: Initiate the automatic zero setting device by: Applying a load of 5e Zero the instrument using the zero setting device and remove the load Wait for the automatic zero setting to occur and the indication displays zero , this should take a minimum of 5 seconds Note: if the indication does not change after 15 seconds , the instrument does not have automatic zero setting and should be tested as semi-automatic zero setting Quickly apply a load of 10e to the load receptor Lightly apply an additional 0.25e

Zero setting device accuracy Automatic zero setting continued If the indication changes and stabilises at +1e from the original indication then the instrument fails If the indication remains unchanged firmly apply an additional 0.5e If the indication changes and stabilises at +1e from the original indication the instrument passes If the indication remains unchanged the instrument fails

Zero setting device accuracy Non-self indicating Instrument ( eg. Steelyard weighing instrument) It is essential that the instrument is set on zero before any tests are performed After completing any test , remove the load and visually check that the instrument has returned within ± 0.25e of its equilibrium position. If it has not returned to its equilibrium position apply 0.25e to the load receptor. Then: If the indicator moves through its equilibrium point , the instrument passes If the indicator does not move through its equilibrium point , the instrument fails

Zero setting device accuracy Analogue indicating instrument It is essential that the instrument is set on zero before any tests are performed After completing any test , remove the load and visually confirm that the instrument has returned to within ± 0.25e of zero

Zero Setting Devices That’s the End of the presentation Are there any questions? Thankyou