美国零长度金属弹簧重力仪（ZLS）  
1991年由Lacoste博士发起创办了——零长度金属弹簧重力仪（ZLS）公司。ZLS公司花费了6年以上的时间开发了这种新的金属零长度弹簧重力仪—贝尔雷斯（Burris）重力仪。
贝尔雷斯（Burris）重力仪不是在过去Lacoste重力仪产品技术的重新包装，而是采用了数字技术的最新发展，使得仪器具有最先进数字性能且易于使用，是目前市场上最准确、精确、耐用和快速读数的重力仪。
通过UltraGravTMControl 电子装置自动操控贝尔雷斯重力仪（Burris Gravity MeterTM）可以达到微伽级精度，作为Lacoste型号的升级换代产品，几年来该产品销售遍及世界各国，获得了世界各国重力使用者的好评。
ZLS Corporation is a manufacturer of high precision, metal, zero-length spring gravity meters and products. Products include upgrades for LaCoste & Romberg marine and air gravity meters.
ZLS was founded in 1991 in response to a need for a high-quality company that would provide the latest in state-of-the-art technology for gravity meter instruments. The company was started in Austin, Texas by three individuals with experience in designing and manufacturing gravity meters: Dr. Adams, Larry Burris and Herbert Valliant. Dr. LaCoste suggested that the company be named after his Zero-Length Spring. The name was fitting and the three began working on their first product, an upgrade for LaCoste & Romberg (L&R) S-meters. Since its start, ZLS has continued to develop its products and services and now offers its own line of gravity meter products which include a land gravity meter (Burris Gravity Meter™) and a Marine / Airborne gravity meter (ZLS Dynamic Gravity Meter™). To continue servicing the gravity meter community ZLS also offers a range of state-of-the-art technology products for L&R G, D, ET, and S-meters.