超声波液位计的换能器 (探头) 发出高频超声波 脉冲, 当遇到被测液位表面时, 该声波便被反射回来, 部分反射回波被换能器 (探头) 接收并转换成电信号。从超声波发射到被接收, 其时间 T 与换能器 (探头) 至被测液位的距离 S 成正比。此距离值 S 与声速 C 和传输时间 T 之间的关系可以用公式表示: S=C×T/2。
SHOW FULL COLUMNS FROM `wbt_user_token` [ RunTime:0.001285s ]
SELECT * FROM `wbt_user_token` WHERE `token` IS NULL AND `expire_time` > 1784330995 LIMIT 1 [ RunTime:0.000373s ]
SELECT * FROM `wbt_user_token` WHERE `token` IS NULL AND `expire_time` > 1784330995 LIMIT 1 [ RunTime:0.000207s ]
SHOW FULL COLUMNS FROM `wbt_goods` [ RunTime:0.001143s ]
SELECT * FROM `wbt_goods` WHERE ( `id` = 908 ) AND `wbt_goods`.`delete_time` IS NULL LIMIT 1 [ RunTime:0.000401s ]
SHOW FULL COLUMNS FROM `wbt_goods_collect` [ RunTime:0.000835s ]
SELECT * FROM `wbt_goods_collect` WHERE `user_id` = 0 AND `goods_id` = 908 [ RunTime:0.000415s ]
SHOW FULL COLUMNS FROM `wbt_goods_compare` [ RunTime:0.001148s ]
SELECT * FROM `wbt_goods_compare` WHERE `user_id` = 0 AND `goods_id` = 908 [ RunTime:0.000257s ]
SHOW FULL COLUMNS FROM `wbt_brand` [ RunTime:0.000854s ]
SELECT `id`,`title`,`title_en`,`config_type`,`price_type` FROM `wbt_brand` WHERE `id` = 2 LIMIT 1 [ RunTime:0.000406s ]
SHOW FULL COLUMNS FROM `wbt_goods_cate_relation` [ RunTime:0.000779s ]
SELECT * FROM `wbt_goods_cate_relation` WHERE `goods_id` = 908 LIMIT 1 [ RunTime:0.000346s ]
SHOW FULL COLUMNS FROM `wbt_goods_data` [ RunTime:0.000822s ]
SELECT * FROM `wbt_goods_data` WHERE `id` = 908 LIMIT 1 [ RunTime:0.000356s ]
SHOW FULL COLUMNS FROM `wbt_goods_attr_relation` [ RunTime:0.000780s ]
SELECT `attr_id`,`attrvalue` FROM `wbt_goods_attr_relation` WHERE `goods_id` = 908 [ RunTime:0.000273s ]
SHOW FULL COLUMNS FROM `wbt_goods_goods_relation` [ RunTime:0.000794s ]
SELECT `goods_id2` FROM `wbt_goods_goods_relation` WHERE `goods_id` = 908 [ RunTime:0.000248s ]
SHOW FULL COLUMNS FROM `wbt_goods_file_relation` [ RunTime:0.000731s ]
SELECT `file_id` FROM `wbt_goods_file_relation` WHERE `goods_id` = 908 [ RunTime:0.000296s ]
SHOW FULL COLUMNS FROM `wbt_goods_video_relation` [ RunTime:0.000767s ]
SELECT `video_id` FROM `wbt_goods_video_relation` WHERE `goods_id` = 908 [ RunTime:0.000260s ]
SHOW FULL COLUMNS FROM `wbt_goods_cate` [ RunTime:0.000910s ]
SELECT `id`,`pid`,`logo`,`logo_active`,`name`,`name_en`,`info` FROM `wbt_goods_cate` WHERE `id` = 50 LIMIT 1 [ RunTime:0.000329s ]
SELECT `id`,`pid`,`logo`,`logo_active`,`name`,`name_en`,`info` FROM `wbt_goods_cate` WHERE `id` = 4 LIMIT 1 [ RunTime:0.000168s ]
SELECT `id`,`pid`,`logo`,`logo_active`,`name`,`name_en`,`info` FROM `wbt_goods_cate` WHERE `id` = 97 LIMIT 1 [ RunTime:0.000139s ]
SHOW FULL COLUMNS FROM `wbt_file` [ RunTime:0.000708s ]
SELECT `id`,`cate_id`,`title`,`file`,`lang` FROM `wbt_file` WHERE `status` = 1 AND `id` IN (3755,3756) ORDER BY `sort` DESC,`id` DESC LIMIT 0,2 [ RunTime:0.000360s ]
