皮带速度是否准确到您的传送带秤系统？

There have been several reports recently that the conveyor belt speed used by the belt scale system controller does not match the belt speed when checked by another method. The reported difference has been as much as 4-5%. I decided to investigate the cause(s) of the difference because any belt speed error in the controller is an equivalent accuracy error for the belt scale system unless a correction is made.

有几个因素有助于皮带速度误差，包括但不限于：

1. Incorrect scale factors used to convert the speed sensor signal to the belt speed
2. Faulty speed sensors or speed sensor installation
3. An error in the comparison method used to check the belt speed reported by the controller.

本文将关注的因素one: incorrect scale factors used to convert the speed sensor signal to belt speed.

First a little background information. Many belt scale systems include two sensors: the load sensor, or the weighbridge, and the speed sensor. The signal from each sensor sent is sampled multiple times per second by the controller, or the integrator. The integrator calculates the instantaneous rate output using this formula:

r = l x s，在哪里

r =瞬时速率

L = instantaneous belt load sampled from load sensor (weighbridge)

S =从速度传感器采样的瞬时带速度。

The instantaneous rate output from the controller is one of the process variables of interest to the plant operator. The controller integrates the calculated instantaneous rate values over time to determine the total amount of product that has passed across the scale. Total production across the scale is another process variable that may be of interest to the plant operator. From the above formula, it is reasonable to conclude that any error in the conveyor belt speed compounds any error with the load signal. The first way to resolve your belt speed issue is to acquire the belt speed accurate prior to addressing any of your load sensor accuracy issue(s).

输送带秤上使用了许多类型的速度传感器。速度传感器通常始终连接到非驱动皮带轮的轴上与传送带接触。输出信号是在赫兹（Hz）中测量的方波电压脉冲。皮带秤系统控制器读取频率信号并将其重新缩放以表示皮带速度。比例因子称为“速度常数”。有关如何编程“速度常数”的说明位于制造商的用户手册中。皮带轮圆周和每次旋转的脉冲（PPR）是影响“速度常数”的两个变量。PPR列在速度传感器的铭牌上。什么应该用于皮带轮围绕？

皮带规模制造商建议使用耦合皮带轮的直径来计算圆周。一个可以解释该陈述以表示在带轮的一端测量的滑轮直径，或者在传送器规格板/绘图上列出了任何直径。这可能并不总是准确。

为确保准确性，考虑这些要点：

1. 一些非驱动的输送带滑轮被撞到冠上以帮助追踪皮带。中心的直径比与末端相比（见图1和2）相比较大。滑轮圆周基于使用最大的皮带轮直径。
2. One manufacturers’ standard “hydro-crowned” pulley is tapered 1/8-inch per foot of width on the diameter or 1/4-inch maximum. The nominal pulley diameter is given at both ends and will have a larger diameter in the center.
3. 来自另一种制造商的加工冠滑轮使用“1/8英寸x 8英寸，从半端逐渐逐渐逐渐缩小滑轮宽于24英寸。”标称滑轮直径在中心给出，末端的皮带轮将更小。
4. 带制造商建议使用“俯仰线直径”来计算滑轮围绕。进一步解释间距线直径以在皮带轮缠绕时在皮带的质心上拍摄的测量。
5. The belt manufacturer further explains that the centroid of the belt is where the belt is neither in compression or tension when it is wrapped around a pulley. Since the belt carcass cannot stretch or compress, consider using the centerline of the carcass as the centroid distance. Please reference figures 1, 2 and 3.

Let’s quantify the accuracy error by using the above points in an example. For example, if:

• Coupled pulley details: 16in dia x 38in wide, machined crown, 3/8in thk lagging
• Belt details: 36in wide, 2-ply, 220piw, 3/16x1/16in SBR covers, 11/32in overall thickness
• 速度传感器是256ppr编码器。

当速度传感器耦合到与带底盖接触的滑轮（图1）距离底盖的皮带距离（图3）=（（S1-S2-S3）/ 2）+ S2（公式1）

= 0.109

When the speed sensor is coupled to a pulley in contact with the top cover per Figure 2:

距顶盖的皮带质心（图3）=（（S1-S2-S3）/ 2）+ S3（公式2）

= 0.234in

If the belt scale commissioning agent uses the circumference at the end of the pulley, then the

circumference measurement may be based on as little as 15-3/4in diameter for the pulley details given above when the lagging thickness is also ignored.

“速度常数”=（256个/ rev /（πx 15.75in / rev））x 12in / ft。= 62.1Pulses / ft。

When the installation is per Figure 1 and formula 1 applies:

• Pitch Line Diameter = 16 + (2 x (3/8 + 0.109)) = 16.97in
• “Speed Constant” = (256 / (π x 16.97)) x 12 = 57.6pulses/ft., which is a 7.8% difference

The difference can be even more for an installation where formula 2 applies:

• Pitch line diameter = 16 + (2 x (3/8 + 0.234)) = 17.22in
• “Speed Constant” = (256 / (π x 17.22)) x 12 = 56.8pulses/ft., which a 9.3% difference

以上分析是为什么报告的皮带速度与另一个的速度比较的解释

方法可以不同。收集基于使用“俯仰线直径”来收集计算圆周所需所需的所有细节可能是不实际的。因此，对于大多数皮带尺度安装，具有另一种检查皮带速度以与皮带速度进行比较的方法是谨慎的

每个控制器。

根据需要进行控制器中的“速度常数”调整，以便在加载负载传感器信号精度差异之前获得皮带速度。