diff --git a/main/echem.c b/main/echem.c
index cb20334..964029f 100644
--- a/main/echem.c
+++ b/main/echem.c
@@ -327,7 +327,14 @@ int echem_clean(float v_mv, float duration_s)
     AD5940_LPDAC0WriteS(code, VZERO_CODE);
 
     printf("Clean: %.0f mV for %.0f s\n", v_mv, duration_s);
-    vTaskDelay(pdMS_TO_TICKS((uint32_t)(duration_s * 1000.0f)));
+
+    uint32_t remain_ms = (uint32_t)(duration_s * 1000.0f);
+    while (remain_ms > 0) {
+        uint32_t chunk = remain_ms > 3000 ? 3000 : remain_ms;
+        vTaskDelay(pdMS_TO_TICKS(chunk));
+        remain_ms -= chunk;
+        if (remain_ms > 0) send_keepalive();
+    }
 
     echem_shutdown_lp();
     AD5940_AFECtrlS(AFECTRL_ALL, bFALSE);
@@ -497,7 +504,15 @@ static uint32_t sample_phase(float v_mv, float t_dep_ms, float t_meas_ms,
     AD5940_LPDAC0WriteS(mv_to_vbias_code(v_mv), VZERO_CODE);
 
     /* settling — no samples recorded */
-    vTaskDelay(pdMS_TO_TICKS((uint32_t)t_dep_ms));
+    {
+        uint32_t remain_ms = (uint32_t)t_dep_ms;
+        while (remain_ms > 0) {
+            uint32_t chunk = remain_ms > 3000 ? 3000 : remain_ms;
+            vTaskDelay(pdMS_TO_TICKS(chunk));
+            remain_ms -= chunk;
+            if (remain_ms > 0) send_keepalive();
+        }
+    }
 
     /* measurement — sample at ~50ms intervals */
     uint32_t n_samples = (uint32_t)(t_meas_ms / 50.0f + 0.5f);
@@ -541,7 +556,15 @@ int echem_chlorine(const ClConfig *cfg, ClPoint *out, uint32_t max_points,
 
     printf("Cl: conditioning at %.0f mV for %.0f ms\n", cfg->v_cond, cfg->t_cond_ms);
     AD5940_LPDAC0WriteS(mv_to_vbias_code(cfg->v_cond), VZERO_CODE);
-    vTaskDelay(pdMS_TO_TICKS((uint32_t)cfg->t_cond_ms));
+    {
+        uint32_t remain_ms = (uint32_t)cfg->t_cond_ms;
+        while (remain_ms > 0) {
+            uint32_t chunk = remain_ms > 3000 ? 3000 : remain_ms;
+            vTaskDelay(pdMS_TO_TICKS(chunk));
+            remain_ms -= chunk;
+            if (remain_ms > 0) send_keepalive();
+        }
+    }
 
     printf("Cl: free chlorine at %.0f mV\n", cfg->v_free);
     idx = sample_phase(cfg->v_free, cfg->t_dep_ms, cfg->t_meas_ms,
@@ -579,7 +602,14 @@ int echem_ph_ocp(const PhConfig *cfg, PhResult *result)
     AD5940_ADCBaseCfgS(&adc);
 
     printf("pH: stabilizing %0.f s\n", cfg->stabilize_s);
-    vTaskDelay(pdMS_TO_TICKS((uint32_t)(cfg->stabilize_s * 1000.0f)));
+
+    uint32_t remain_ms = (uint32_t)(cfg->stabilize_s * 1000.0f);
+    while (remain_ms > 0) {
+        uint32_t chunk = remain_ms > 3000 ? 3000 : remain_ms;
+        vTaskDelay(pdMS_TO_TICKS(chunk));
+        remain_ms -= chunk;
+        if (remain_ms > 0) send_keepalive();
+    }
 
     /* average N readings of V(SE0) and V(RE0) */
     #define PH_AVG_N 10